Mexican Fish Ceviche Tostadas with Avocado

Why You’ll Love This Recipe

• Bright, fresh flavors with a classic Mexican profile: lime, chile, cilantro, and creamy avocado.
• No stove required—acid “cooks” the fish for a crisp, refreshing meal.
• Ready in under an hour, most of it hands-off marinating time.
• Perfect for warm-weather gatherings; easy to scale for a crowd.

Grocery List

• Produce: Limes (8–10), Roma tomatoes (2–3), Persian/English cucumber (1 large), red onion (1 small), serrano chiles (1–2), cilantro (1 bunch), avocado (1), garlic (1 small clove, optional), extra limes for serving
• Dairy: None
• Pantry: Kosher salt, sugar, black pepper, extra-virgin olive oil, tostada shells (or corn tortillas + neutral oil), hot sauce (Valentina or Cholula)

Full Ingredients

Ceviche Base

• 1.25 lb (570 g) very fresh, firm white fish (halibut, snapper, sea bass, or mahi-mahi), skinless and boneless, cut into 1/2-inch (1.3 cm) dice
• 1 cup (240 ml) fresh lime juice (about 8–10 juicy limes)
• 1 tsp kosher salt
• 1/2 tsp sugar (balances lime bitterness)
• 1/4 tsp freshly ground black pepper
• 1 small garlic clove, finely grated or minced (optional)

Vegetables & Herbs

• 1 cup small-dice Roma tomato, seeded (about 2 medium)
• 1 cup small-dice cucumber, peeled (Persian or English)
• 1/2 cup finely diced red onion
• 1–2 serrano chiles, finely minced (seeded for less heat), 2–4 tsp total
• 1/2 cup roughly chopped fresh cilantro (tender stems and leaves)
• 1 medium avocado, 1/2-inch dice
• 2 tbsp extra-virgin olive oil

For Serving

• 8 tostada shells (store-bought) or 8 corn tortillas to crisp
• Hot sauce (Valentina, Cholula, or your favorite)
• Lime wedges

Step-by-Step Instructions

Step 1: Prep and chill the fish

Pat the fish very dry with paper towels. Trim away any dark muscle or membranes for the cleanest flavor, then cut into neat 1/2-inch dice. Keep the fish chilled while you prepare the marinade.

Step 2: Marinate in lime until “cooked”

In a non-reactive bowl (glass or stainless steel), combine lime juice, kosher salt, sugar, black pepper, and garlic (if using). Add the fish and stir to fully submerge. Cover and refrigerate for 30 minutes, stirring once halfway. The fish should turn opaque around the edges and slightly firm; a small cube should flake when pressed. Do not over-marinate or the texture can become chalky.

Step 3: Prep crisp, fresh add-ins

While the fish marinates, dice the tomato and cucumber, finely dice the red onion, mince the serranos, and chop the cilantro. For a milder onion bite, rinse the diced onion under cold water and pat dry. Keep everything chilled. Dice the avocado last, right before combining.

Step 4: Drain and combine

Drain off most of the lime juice from the fish, leaving about 2 tablespoons in the bowl to keep things bright and juicy. Add tomato, cucumber, red onion, serrano, cilantro, and olive oil. Gently fold to combine. Taste and adjust salt and lime to your liking.

Step 5: Fold in avocado

Gently fold in the diced avocado so it holds its shape. If you like it creamier, lightly mash a few cubes against the side of the bowl to enrich the juices.

Step 6: Crisp the tostadas (if making your own)

To bake: Preheat the oven to 375°F (190°C). Brush 8 corn tortillas lightly with neutral oil, place on a sheet pan, and bake 7–9 minutes, flipping once, until deeply crisp. Cool completely so they stay crunchy. Alternatively, toast in a dry skillet over medium-high heat 60–90 seconds per side until crisp.

Step 7: Assemble and serve

Top each tostada with a generous scoop of ceviche, letting a little of the limey juices kiss the edges. Drizzle with hot sauce to taste and garnish with extra cilantro. Serve immediately with lime wedges. Keep any extra ceviche chilled and build tostadas to order so they stay crisp.

Pro Tips

• Fish freshness first: Use very fresh fish that has been previously frozen (parasite control) and keep everything cold from start to finish.
• Right-size your dice: 1/2-inch cubes give a tender bite and “cook” evenly in about 30 minutes.
• Seed watery veg: Seed tomatoes and peel cucumbers to keep the ceviche bright, not watery.
• Drain before dressing: Pour off most of the lime juice before adding veg so the tostadas don’t get soggy.
• Adjust heat smartly: Remove chile seeds and ribs for mild heat; leave some in or use 2 serranos for a classic kick.

Variations

• Shrimp and fish combo: Use 10 oz fish + 10 oz small shrimp. Quickly blanch shrimp 60 seconds, chill, then marinate with the fish.
• Tropical twist: Add 1/2 cup finely diced ripe mango or pineapple for sweet contrast with the lime and chile.
• Sinaloa-style vibes: Stir in 2–3 tbsp tomato juice or Clamato for a juicier ceviche and a splash of color.

Storage & Make-Ahead

Prep the vegetables up to 6 hours ahead and keep them chilled in separate containers. Marinate the fish for about 30 minutes right before serving, then drain and combine with the veg. Fold in avocado at the very end. Assembled tostadas should be eaten immediately. Store leftover ceviche (without avocado, if possible) tightly covered in the refrigerator for up to 24 hours; re-fresh with a squeeze of lime and a pinch of salt. Food safety note: Lime juice firms and denatures the fish but does not pasteurize it—use high-quality fish, keep it cold, and enjoy promptly.

Nutrition (per serving)

Approximate values for 1 serving (2 tostadas with toppings): 420 calories; 30 g protein; 18 g fat; 35 g carbohydrates; 6 g fiber; 550 mg sodium. Values will vary based on fish choice, tostada brand, and hot sauce.