In a large skillet over medium-high heat, add 1 pound of ground beef. Cook until browned, breaking it apart with a spatula for even cooking, about 5-7 minutes. Stir in 2 tablespoons of tomato paste and seasonings like salt, pepper, and cumin, mixing until fully combined. Drain any excess fat, and let the filling cool slightly while you assemble the quesadillas.

Lay a flour tortilla flat on a clean surface. On one half, sprinkle a generous layer of sharp cheddar cheese, followed by the seasoned ground beef mixture, and a sprinkle of Monterey Jack cheese. Carefully fold the tortilla over the filling, pressing down gently to seal it. Repeat this process with remaining tortillas to create a stack of quesadillas.

Heat a heavy skillet or cast iron pan over medium heat. Once hot, add a folded quesadilla and cook for 2-3 minutes, or until the bottom side turns golden brown and crispy. Carefully flip the quesadilla using a spatula, cooking the other side for an additional 2-3 minutes, until the cheese is melted and both sides are nicely browned.

Once cooked, transfer the quesadilla to a cutting board and allow it to rest for 1 minute. This brief pause helps firm up the layers before cutting. Use a sharp knife or pizza cutter to slice the quesadilla into wedges, making it easier to serve and enjoy the delicious ground beef quesadilla filling.

Arrange the quesadilla wedges on a serving platter, garnishing with freshly chopped cilantro if desired. Serve hot with sour cream and any favorite sides like guacamole or pico de gallo for added flavor.