Preheat oven to 325 degrees.
Mix together melted butter, garlic salt, and 1/4 teaspoon chili powder.
Cut tortillas with a 3-inch biscuit cutter or cookie cutter. You should get 3-4 circles per tortilla. Stack tortillas, wrap in a moist paper towel, and microwave for 20 seconds to soften.
Brush both sides of tortilla circles with butter mixture and press into cups of a mini muffin pan so that they take the shape of the muffin cup.
Bake for 15-18 minutes. Cool in pan 5 minutes and then remove to wire rack to cool completely.
In a large nonstick skillet over medium-high heat, cook ground beef, breaking it up with a wooden spoon. When most of the pink is gone add onion. Cook 2 more minutes.
Add chili powder, cumin, and cayenne pepper. Stir for 30 seconds and then add tomato sauce. Simmer until thickens and then season to taste with salt and pepper.
Place refried beans and cheese in a small microwave safe bowl. Heat 30 seconds and stir. If cheese is not fully melted, heat in 20 second increments until cheese melts.
Place a small amount of bean mixture on bottom of each taco shell. Top with small spoonful of meat mixture.
Sprinkle with lettuce, tomato, red onion, avocado, and cilantro. Add small dollop of sour cream.