Heat a large skillet over medium-high heat.
Add the ground beef to the skillet and cook, breaking it apart with a spatula, until browned and no longer pink, about 5 to 7 minutes.
Drain excess fat from the skillet if necessary.
Add the chopped onion and minced garlic to the skillet with the beef; cook until the onion is softened, about 3 minutes.
Stir in chili powder, ground cumin, smoked paprika, crushed red pepper flakes, salt, and black pepper. Cook for 1 minute to toast the spices.
Pour in the tomato sauce and stir to combine. Reduce heat to medium-low and simmer for 5 minutes, stirring occasionally.
While the beef mixture simmers, warm the flour tortillas in a dry skillet or microwave until pliable.
To assemble tacos, spoon the beef mixture evenly onto each tortilla.
Top each taco with shredded cheddar cheese, shredded lettuce, diced tomato, and chopped cilantro.
Add a dollop of sour cream on top and serve with lime wedges on the side for squeezing over the tacos.