Preheat oven to 450°F (230°C). Coat a large, rimmed baking sheet with oil or nonstick spray.
Prepare the Fajita Seasoning
In a small bowl, stir together paprika, chili powder, salt, cumin, onion powder, garlic powder, oregano, and cayenne.
Season the Steak and Vegetables
Arrange steak in the center of the prepared sheet pan, with the bell peppers and onion in a single layer around the edges. Drizzle the veggies with olive oil; toss to coat. Rub olive oil on both sides of the steak as well.
Sprinkle the vegetables with the seasoning blend; toss to coat again. Rub additional seasoning into both sides of the meat. You might not need all of the seasoning for this meal, so if you have some extra you can set it aside in an airtight container in the pantry for up to 3 months.
Bake the Steak and Vegetables
Bake for 12-15 minutes, or until the steak reaches the desired level of doneness and the vegetables are crisp-tender, stirring the veggies halfway through and flipping over the steak. A meat thermometer should read 125-130°F for rare, 135°F for medium rare, and 145°F for medium. Drizzle the meat and vegetables with lime juice. Remove the steak from the pan and place on a cutting board. Tent loosely with aluminum foil while the steak rests for 5-10 minutes. Slice the steak against the grain of the meat (perpendicular to the lines that you see), on a diagonal.
Serve the Fajitas
Serve the sliced steak with the vegetables in warm tortillas with all of your favorite toppings.
Video
Notes
To easily warm tortillas before serving, wrap the stack of tortillas in foil and place them in the oven during latter half of the baking time. Alternatively, you can microwave the tortillas on a plate under a damp paper towel until warmed through.