Divide ground beef into 8 two ounce meatballs. Use a kitchen scale so you get evenly sized pieces of beef. Set aside.
Prepare burger sauce.
Prepare produce. Shred lettuce, dice tomatoes, slice red onion. Set aside.
Heat a grill or large skillet over medium high heat.
Once grilll is hot place a meatball on the hot grill and use a heavy duty spatula to "smash" the ball into a flat, really thin patty. Keep pressing until the patty is the size of the flour tortilla.
Season beef patty generously with salt and pepper.
Top the patty with a slice of cheese.
Top with a tortilla and press the tortilla into the beef patty and slice of cheese on the grill.
When beef patty is cooked through and crispy along the edges, about 2-3 minutes, then flip it over.
Top with another slice of cheese. Continue to cook for another 1-2 minutes to melt cheese.
Move off heat and keep warm while you repeat the process to make another burger.
Once cheese is soft and melty, transfer the taco burger to a plate and top it with shredded lettuce, diced tomato, sliced red onion and a drizzle of burger sauce.
Serve immediately.