Wash and dry all produce. Peel, halve, and thinly slice onion. Mince a few slices until you have 2 TBSP minced onion. Core, seed, and thinly slice yellow and green bell peppers. Core, then finely chop tomatoes. Finely chop cilantro. Cut lime in half; cut one half into wedges.

Heat a large drizzle of olive oil in a large pan over medium-high heat.Add sliced onion and bell peppers. Season with salt and pepper. Cook, tossing occasionally, until softened and charred in spots, 10-12 minutes. Remove from pan and set aside.

Combine tomatoes, half the cilantro, minced onion, juice from lime half, and a drizzle of olive oil in a medium bowl. Season with salt and pepper.

Pat beef dry with a paper towel. Heat a large drizzle of olive oil in pan used for veggies over medium-high heat. Add beef and season with fajita spice, salt, and pepper. Cook, tossing occasionally, until browned and cooked to desired doneness, 3-5 minutes.

Wrap tortillas in a damp paper towel and microwave on high until warm, about 30 seconds. TIP: Alternatively, wrap tortillas in foil and warm in oven for 5 minutes at 400 degrees.

Divide cheddar between tortillas, then top each with the beef, veggies, and salsa. Dollop with sour cream and sprinkle with remaining cilantro. Serve with lime wedges for squeezing over.