Sheet Pan Steak Fajitas

Name: Sheet Pan Steak Fajitas
Ingredients: 2 pounds flank steak; salt and fresh ground pepper to taste; 3 tablespoons homemade fajitas seasoning mix divided; 1-1/2 tablespoons olive oil divided; 1 red bell pepper cut into strips; 1 green bell pepper cut into strips; 1 yellow bell pepper cut into strips; 1 red onion thinly sliced; 12 (6-inch) Whole Wheat Low Carb Flour Tortillas; chopped fresh parsley or cilantro for garnish; lime slices for garnish; plain yogurt or sour cream optional, for garnish; shredded cheddar cheese optional, for garnish; avocado diced, for garnish