1 pounds shrimp – peeled, deveined, and cut into 0.5-inch pieces
10 limes – juiced (about 1 cup juice)
1 orange – juiced (0.25 cup juice)
1 tsp kosher salt
0.5 cup red onion – finely chopped
1 serrano chile – finely chopped (seeds removed if desired)
1 cup cucumber – peeled, seeded, and diced
1 cup tomato – diced
0.5 cup cilantro leaves and tender stems – chopped
avocado – diced (for serving)
tostadas – for serving
Instructions
Prepare the shrimp: Peel and devein if needed, then cut into 0.5-inch pieces.
Juice the limes and the orange; measure about 1 cup lime juice and 0.25 cup orange juice.
In a nonreactive glass or ceramic bowl, combine the shrimp with the lime juice, orange juice, and kosher salt. Press the shrimp down so it’s submerged. Cover and refrigerate until the shrimp turns opaque and just firm, 25–35 minutes, stirring once halfway.
While the shrimp cures, finely chop the red onion and serrano, dice the cucumber and tomato, and chop the cilantro.
Drain off most of the citrus from the shrimp, leaving about 0.25 cup in the bowl. Add the red onion, serrano, cucumber, tomato, and cilantro; toss gently to combine.
Serve immediately spooned onto tostadas and topped with diced avocado.