Step 1

Peel and devein the shrimp, and then slice them in half longwise.

Step 2

Add shrimp to a non-reactive (metal or glass) bowl, and set aside.

Step 3

Squeeze the juice from four limes.

Step 4

Blend lime juice, 2 jalepeños, 1 cup of cilantro, 1 tsp of salt in a blender until smooth

Step 5

Add mixture to bowl with shrimp, mixing well to make sure the shrimp is covered.

Step 6

Cover, and place in refrigerator for 20 minutes. *

Step 7

Peel the cucumber, cut it in half lengthwise. Remove the seeds with a spoon and cut it into slices.

Step 8

Thinly slice the 1/2 purple onion.

Step 9

Mix cucumber with the shrimp, and serve on tostadas, topping with sliced red onion.