Preheat oven to 475 degrees F and line 2 large baking sheets with unbleached parchment paper. Transfer steak and vegetables into 2 separate piles on one sheet pan.
Steak: Drizzle with olive oil and lime juice, top with jalapeno, then sprinkle with taco seasoning, garlic powder, salt and pepper.
Vegetables: Drizzle with olive oil and season with taco seasoning, salt and pepper.
Toss each pile separately, then mix meat and veggies together and transfer half of steak fajitas on second sheet. Spread in a single layer on both sheets.
Bake for 20 minutes. To check for doneness, just taste a piece of steak. Then broil until golden brown, about 5 minutes.
Remove from the oven and season steak only with a pinch of pink, coarse or regular salt. I underseason fajitas during cooking on purpose because a small sprinkle of salt at the end is everything.
Serve steak fajitas hot in tortillas with your favorite toppings.
Notes
Store:Refrigerate leftovers in an airtight container for up to 3 days. To reheat, throw on a non-stick skillet and pan fry until warmed through. It will give fajitas an extra char and refresh them.
Different baking sheet: Dark colored baking pan might cook fajitas faster.
Ovens vary: If you have convection oven by default, it will cook fajitas faster as well.
More heat: Leave some seeds in jalapeno for a heat kick.