• Preheat the oven to 475°.
• Zest the limes and then slice in half. Slice one lime half into small wedges and reserve one per person for garnish.
• Wash and dry the jalapeños and slice into thin rounds. 
• Wash, pat dry, and slice the zucchini with a mandolin or knife into very thin slices.
• Peel, and finely dice the garlic.
• Wash, pat dry, and coarsely chop the cilantro. You should have about 1/3 cup. *Reserve 1 tbsp for garnish.
  
• To a medium bowl add the cleaned, dry shrimp, garlic, ½ of the zest, and ½ of the cilantro.
• Add a sprinkle of salt, pepper and add a pinch of granulated onion, red pepper flakes, and/or cumin if desired.
• In a small bowl covered with a paper towel, melt butter carefully in the microwave in ten-second increments. Just until it's melted, but not hot. Stir in the olive oil.
• Add about 1½ tbsp melted but not hot butter/oil mixture to the bowl with the shrimp.
  
• Squeeze juice from limes over the shrimp, mix and allow it to marinate for just a couple minutes while you prepare the pan and topping.
  

Prepare the Panko Topping (Scroll down for instructions for serving leftover)

• Add the panko, 2 tbsp butter/oil mixture, cilantro, and remaining lime zest to a bowl and stir. Add salt and pepper to taste, and a sprinkle of granulated onion to taste.
  

Prepare the Dish

• Lightly oil the bottom and sides of a large cast-iron skillet. Add the zucchini slices and season with granulated onion, salt and pepper to taste. Arrange them in a thin layer around the perimeter of the pan, and up the sides.
  
• Line the middle of the cast iron pan with jalapeno slices. (and/or scallions)
  
• Place the shrimp in a flat, single layer on top of the jalapenos, and pour the marinade over the top. The butter may have solidified some, just spoon it over the shrimp.
  
• Spoon panko topping evenly over the shrimp and drizzle the remaining butter/oil over the top of the zucchini and panko.

  (If you are serving a portion of the dish as leftovers, set aside some of the panko topping.)
• Bake the shrimp skillet in the preheated 475° oven for about seven to ten minutes, or until shrimp are pink and topping gets browned. If you're not sure, remove one and cut it in half after about seven minutes. If it is cooked, it will be pink and slightly white in the center.
  

To Prepare Panko Topping to Serve Leftover

• Brown the seasoned panko in butter/oil in a skillet over medium-high heat until lightly toasted. Mix in the cilantro and zest and set aside. When cool, place toppings in zip-top or small containers to top the shrimp later!