How to Make It
Preheat oven to 200°F. Heat 1 teaspoon of the oil in a large skillet over medium-high. Add ground chuck, onion, garlic, and salt; cook, stirring occasionally, until beef is browned and cooked through, 6 to 8 minutes. Add taco seasoning mix and tomato paste; cook, stirring constantly, until fragrant and toasted, about 1 minute. Remove beef mixture, and drain. Do not wipe skillet clean.
Sprinkle each tortilla evenly with 1/2 cup cheese, and top each with 3/4 cup meat mixture; fold tortillas in half. Heat 1 teaspoon of the oil in a large nonstick skillet over medium; add 2 quesadillas, and cook until golden brown and crisp, 1 to 2 minutes. Using a spatula, turn quesadillas over, and cook 1 more minute. Transfer hot quesadillas to a baking sheet, and keep warm in preheated oven. Repeat with remaining 1 teaspoon oil and 2 quesadillas. Serve with sour cream, guacamole, and salsa.