Preheat the oven to 425 degrees F. Butter a large baking sheet.
Cook, crumble and brown 1 pound lean ground beef along with 1 teaspoon salt, ½ teaspoon black pepper, 1 teaspoon onion powder and ¼ teaspoon cayenne pepper. Drain any excess grease (there shouldn't be much if you used lean meat.)
Place 8 of the 10 taco size flour tortillas on the cookie sheet (2 at the end and 6 around the edges)
Looking at the 2 tortillas at the end, imagine a rectangle and spread the cooked ground beef in an even layer down the middle.
Sprinkle 1 cup shredded mozzarella cheese over the meat layer
In a pan (I used the same pan I cooked the meat with) warm up the ⅓ cup finely diced red onion and ⅔ cup diced bell peppers for 4 minutes over medium heat. Spread the onion/pepper mixture over the cheese.
Evenly sprinkle 1 cup shredded cheddar cheese over the onions and peppers layer.
Butter the 2 remaining tortillas with 2 Tablespoons salted butter, melted and place over the cheese to cover the center (butter side up.)
Fold the side tortillas over the buttered tortillas. Press gently. The butter will act as the glue.
Finish by folding the end tortillas and gently press. You can spread the rest of the melted butter on the rest of the tortillas.
Optional: if you find the tortillas keep popping up, you can place another cooking sheet on top while it bakes to keep it pressed down. After practice, I have found this really helps.
Cook in the preheated oven for 15 to 17 minutes until crisp and golden brown. Slice and enjoy with your favorite toppings (sour cream, salsa, jalapeños, diced tomatoes, etc.)
Notes
If you want the peppers and onions to be softer, just cook them along with the ground beef rather than separately like in Step 6.
Any shredded cheese you like will work. A Mexican shredded cheese blend is also delicious.