Peel and butterfly all of the shrimp, reserving the shells in a separate bowl for later use. Place the prepared shrimp in a bowl and add the grated lime peel, fresh lime juice, kosher salt, and ground black pepper. Stir to combine, then cover and refrigerate the shrimp to marinate in the lime juice for 15 minutes.

While the shrimp marinates, add the reserved shrimp shells and water to a medium-sized saucepan. Bring the water to a boil over medium-high heat and cook the shells until they turn a bright-pink color, about 3 minutes. Remove from heat, strain the shells out to collect the stock, and let the stock cool for about 5 minutes before using.

Peel and roughly chop one large cucumber. Combine the chopped cucumber, cooled shrimp stock from Step 2, packed chopped cilantro, serrano chiles, habanero pepper, garlic cloves, ground cumin, ground coriander, MSG (if using), and about 1/2 cup of the marinating lime juice from the shrimp in a blender. Blend on high until well combined and no large chunks remain. I like to add a little extra cilantro for an extra fresh kick.

Using a fine-mesh strainer, pour the blended liquid from Step 3 over the marinated shrimp from Step 1. Use the back of a large spoon to press and extract as much liquid as possible from the pulp. Discard the leftover pulp once done.

Peel, deseed, and slice the remaining cucumber into 1/8-inch half-moon pieces. Thinly slice half of the red onion. Add these fresh vegetables to the marinated shrimp mixture and stir until all the vegetables are evenly distributed.

Before serving, check that the shrimp is fully cooked; it should be white all the way through with no translucent or gray areas. Taste the mixture and adjust the seasoning if needed—sometimes I like to add an extra squeeze of lime or a pinch more salt to brighten it up. Serve chilled, ideally with tostadas or your favorite crunchy accompaniment.