Spicy Beef Fajita Burger Recipe

Name: Spicy Beef Fajita Burger Recipe
Ingredients: 1 pound ground beef; 1 large egg, room temperature; 1 tablespoon + ½ teaspoon fajita seasoning, divided; Pinch of chili flakes; ⅓ teaspoon onion powder; ¾ teaspoon garlic powder, divided; salt, to taste; pepper, to taste; ½ cup mayonnaise; ¼ cup sour cream; 1 tablespoon fresh coriander, finely chopped; Juice of ½ lime; 1 tablespoon cooking oil; 1 large onion, sliced; 2 red bell peppers, sliced; 6 slices cheddar cheese; 6 burger buns; 1 cup lettuce leaves