1. Combine lime zest, orange zest, chili powder, cumin, garlic powder, onion powder, coriander, ¼ teaspoon sea salt, and sugar in a small bowl. Set chili-lime seasoning aside.
2. Combine rice flour, baking powder, and baking soda in a large bowl. Add egg yolk and seltzer water and whisk until smooth. Season generously with salt and pepper. Heat about 2 cups vegetable oil in a large straight-sided skillet over medium heat. Sprinkle shrimp with a little rice flour. Working in batches, dip shrimp in batter, drip off excess (you want a very thin coating), and fry in oil until golden brown, about 2 minutes per side. Transfer to a wire rack to drain.
3. To serve, combine 2 cups popped popcorn and ¼ of the fried shrimp in a large bowl, drizzle with 1 tablespoon melted butter, sprinkle generously with chili-lime seasoning, and toss to combine. Transfer to a paper bag for serving, if desired. Repeat with remaining popcorn and shrimp.