In a large skillet, heat the oil over medium-low heat. Add the diced onion and jalapeño, and cook, stirring occasionally, until softened, about 5 minutes. Add the minced garlic and cook for an additional 30 seconds.

Add the ground beef, chili powder, cumin, dried oregano, salt, pepper, and drained Rotel tomatoes to the skillet. Stir until well combined, then reduce the heat to low. Simmer, stirring occasionally, until the meat is browned, about 15 minutes. Stir in the lime juice and cilantro, taste, and adjust the seasonings if needed. Remove from heat.

Set a wire rack over a rimmed baking sheet lined with parchment paper for easy cleanup.

In a heavy skillet, heat 2 inches of oil to 350°F.

Add one tortilla to the skillet and cook until it starts to blister but is still soft, about 10 to 15 seconds. Using tongs, turn the tortilla over and immediately fold it in half to form a taco shell.

Once the tortilla holds its shape, continue cooking until it is crisp and golden all over, about 15 to 30 seconds longer. Transfer to the wire rack and keep warm in the oven while you repeat with the remaining tortillas.

Fill each taco shell with the ground beef mixture, shredded lettuce, diced tomatoes, shredded cheddar cheese, diced avocados, and sliced olives. Serve with salsa and sour cream on the side, if desired.