Prepare your seasoned ground beef. If you don't have pre-seasoned beef, cook 1/4 pound of ground beef, drain, and stir in 1 teaspoon chili powder, 1/2 teaspoon cumin, 1/4 teaspoon garlic powder, 1/4 teaspoon onion powder, and a pinch of salt and pepper. Set aside.
Warm one large flour tortilla slightly in a dry skillet over medium heat for about 30 seconds per side. This makes it more pliable. Place the warmed tortilla on a clean surface or plate.
Sprinkle half of the Monterey Jack and half of the Cheddar cheese evenly over the tortilla, leaving a small border. This will be the 'quesadilla' layer.
Carefully place the second large flour tortilla on top of the cheese. This will act as the 'burrito' wrapper.
Heat a large non-stick skillet over medium heat. Add a tiny bit of oil or cooking spray if needed, though a good non-stick pan might not require it.
Place the assembled tortilla stack (tortilla-cheese-tortilla) into the heated skillet. Cook for 2-3 minutes until the bottom tortilla starts to turn golden brown and the cheese begins to melt.
Using a spatula, carefully flip the entire stack over. Cook for another 2-3 minutes until the second side is golden brown and the cheese is fully melted and gooey.
Remove the cheesy tortilla stack from the skillet and place it back on your clean surface, cheese-side up. Let it cool for about 30 seconds.
Now, carefully peel off the top tortilla. You should have a perfectly melted cheese layer underneath. Spread the sour cream and salsa evenly over the melted cheese. Layer the seasoned ground beef, cilantro, and jalapeƱos (if using) on top of the salsa.
Top with the remaining Monterey Jack and Cheddar cheese, followed by the chopped lettuce and guacamole/avocado. Finally, place the reserved top tortilla (the one you peeled off) back on top, pressing down gently.
Carefully slide the entire Quesarito back into the non-stick skillet (you might need to add a tiny bit more oil/spray). Cook for 1-2 minutes per side, pressing gently with the spatula, until golden brown and sealed. This step helps meld everything together.
Slide the finished Quesarito onto a cutting board. Let it rest for a minute before slicing in half with a sharp knife or pizza cutter. Serve immediately.