Heat olive oil in a large skillet over medium-high heat until shimmering, about 1 minute. Add diced onion and cook until softened and translucent, 5 minutes, stirring occasionally to prevent browning on the bottom.

Add minced garlic and cook for exactly 30 seconds until fragrant, then add ground beef to the skillet. Break the meat into small crumbles using a wooden spoon, cooking until completely browned and no pink remains, 8-10 minutes total.

Drain excess fat from the skillet if needed, then add chili powder, cumin, paprika, and cayenne pepper to the cooked beef. Stir constantly for 1 minute to bloom the spices and create that warm cozy fall taco dinner aroma throughout your kitchen.

Pour in beef broth and tomato sauce, stirring well to combine with the spiced meat mixture. Simmer uncovered for 5-7 minutes until the sauce reduces slightly and thickens, adjusting seasoning with salt and pepper to your preference.

Warm the taco shells according to package directions, usually 3-4 minutes in a 350°F oven or 1 minute per side in a dry skillet for stovetop toasting.

Arrange all toppings in small bowls: shredded cheese, lettuce, tomatoes, sour cream, and cilantro so everyone can build their own tacos exactly as desired.

Spoon the warm, seasoned beef mixture into each shell and top with desired ingredients—approximately 3-4 tablespoons of meat per taco shell works perfectly for balanced bites.