Preheat the oven to 375°F.

Lay 2 of the flour tortillas into the bottom of a 9x13 baking dish. Use a sharp knife or pizza cutter to trim the edges for a perfect fit, then use these as a pattern to cut remaining tortillas for the layers.

Spray a 9x13 baking dish with nonstick spray and set aside.

In a saucepan over medium-high heat, cook the ground beef, onion, and garlic until beef is browned and cooked through. Reduce heat to medium-low.

In a small bowl, whisk together taco seasoning and water, then pour over cooked beef mixture. Cook for 2-3 minutes until slightly thickened, stirring often. Remove from heat.

Arrange 2 of the tortillas in the prepared dish. Spread half of the beef mixture over tortillas, then half of the salsa, black beans, and cheese. Repeat layers with remaining tortillas and ingredients.

Bake for 20-25 minutes. Garnish with chopped cilantro. Serve with sour cream and pico de gallo if desired.