There’s a couple ways you can make your ceviche. Traditionally you put raw shrimp in a bowl, add lime/lemon juice and allow the citrus to cook the shrimp before eating. If you’re worried about your shrimp cooking all the way through you could give it a quick dip in boiling water before letting it sit and finishing cooking in lime juice. So, method 1:

1. Cut shrimp in half or leave whole. Place shrimp in a glass bowl and cover with lime juice to marinate (or ‘cook’) for about 10- 30 minutes, or until they turn pink and opaque. 

Or method 2:

1. In a large pot, bring to a boil 2 quarts of water, salted with 1 tablespoons salt. Add the shrimp and cook for 1 minute to 2 minutes max, depending on size of shrimp. (Over-cooking the shrimp will turn it rubbery.) Remove shrimp with a slotted spoon and place into a bowl of ice water to stop the cooking. Drain the shrimp. Cut each piece of shrimp in half, or into inch-long pieces. Place the shrimp in a glass or ceramic bowl. Mix in the lime and lemon juice. Cover and refrigerate for a half hour.

 

1.  Meanwhile, place the onion, pepper, radish, pineapple, and pepper sauces in a separate glass or ceramic bowl. When ready, remove shrimp from lime juice mixture with a slotted spoon, reserving liquid and add to second bowl. Refrigerate an additional half hour.
2. Right before serving add the cilantro and avocado, a little of the leftover lime juice mix and salt to taste. Toss gently to mix
3. Toast tostadas, smear some spicy aioli on it and top with ceviche mix