Heat the olive oil in a large skillet over medium-high heat.
Add the sliced onions and bell peppers to the skillet and sauté for 5-6 minutes until they are tender and slightly caramelized. Remove the vegetables from the skillet and set aside.
In the same skillet, add the ground beef. Cook, breaking it up with a spatula, until browned and cooked through, about 6-7 minutes.
Add the minced garlic, chili powder, ground cumin, smoked paprika, dried oregano, crushed red pepper flakes, salt, and black pepper to the cooked ground beef. Stir well to combine and cook for an additional 1-2 minutes to toast the spices.
Return the sautéed bell peppers and onions to the skillet with the seasoned ground beef. Stir to combine and heat through for 1-2 minutes.
Warm the flour tortillas in a dry skillet or microwave according to package instructions.
To serve, spoon the ground beef and vegetable mixture onto each tortilla. Top with shredded cheddar cheese and chopped fresh cilantro if desired. Serve with lime wedges on the side.