Preheat oven to 375 degrees.
Dice the onion and bell peppers.
In a large skillet, cook the 1 lb ground beef over medium heat, breaking it apart, until no longer pink. Drain grease, to taste. (I leave a little because it has so much flavor.)
Stir in the 1 oz packet of taco seasoning.
Add the onion, red bell pepper, green bell pepper, 15.25 oz can black beans, and 4 oz can green chilies. Stir to combine and cook briefly until the vegetables soften.
Arrange 7 tortillas on a large sheet pan so each tortilla is half on the pan, half off, and slightly overlapping. Place two along each long side, one at the top, one at the bottom, and overlap as needed to cover the pan.
Sprinkle half of the 16 oz colby jack cheese over the tortilla base.
Spread the beef and vegetable mixture evenly over the cheese.
Add the remaining cheese over the filling.
Place the last tortilla in the center, then fold the outer tortillas into the middle to cover the filling.
Set a second sheet pan on top and bake for 20 minutes.
Remove the top sheet pan and bake 15 minutes more, until golden and crisp.
Rest briefly, then cut into 8 squares or 12 smaller pieces. Serve with green onions, sour cream, and salsa.