1. Slice the avocados in half lengthwise and remove the pit. Scoop the flesh out with a spoon into a large bowl. Add garlic, lime juice, and fresh cilantro. Season with salt and black pepper, to taste, and mash with a fork until thoroughly blended and smooth. Cover tightly and set aside.
2. Combine mango, bell pepper, red onion, avocado, cilantro, and fresh lime juice in a medium glass or other non-reactive bowl. Season with salt and black pepper, to taste, and stir to combine. Set aside.
3. Add shrimp to a large bowl and season with chili powder, cumin, and garlic powder. Season with salt and black pepper, to taste, and toss to combine.
4. Heat butter in a large non-stick skillet over medium heat. As the butter melts, swirl to coat the bottom of the pan. Add seasoned shrimp and cook, stirring frequently, until the shrimp becomes opaque and starts to curl, approximately 3-4 minutes. Do not overcook. Remove from heat and set aside.
5. Assemble by adding 1-2 tablespoons guacamole, followed by approximately 3 tablespoons of mango salsa to each cup. Top each appetizer cup with three cooked shrimp and serve immediately with some gluten-free tortilla chips, if desired. Enjoy!