Step 1: Prepare the Vegetables and Seasoning

1. Slice the Vegetables: Thinly slice all your bell peppers, the red onion, and the portobello mushrooms. Place them all together in a large mixing bowl.

2. Mix the Seasoning: In a small bowl, combine all the fajita seasoning ingredients: chili powder, smoked paprika, cumin, garlic powder, onion powder, oregano, salt, black pepper, and cayenne pepper (if using). Whisk until everything is evenly distributed.

3. Season the Vegetables: Drizzle the 2 tablespoons of olive oil over the sliced vegetables in the large bowl. Sprinkle the entire homemade seasoning blend over the top. Use your hands or a pair of tongs to toss everything together thoroughly, ensuring every slice of vegetable is coated in the oil and spices. For the best flavor, you can let this sit and marinate for 15-20 minutes at room temperature, but this step is optional if you’re in a hurry.

Step 2: Cook the Fajita Skillet

1. Heat the Skillet: Place a large cast-iron skillet or other heavy-bottomed frying pan over medium-high heat. Let the pan get very hot. A hot pan is essential for achieving that classic fajita char and sizzle.

2. Cook in Batches: Add a small drizzle of oil to the hot skillet. Working in two or three batches to avoid overcrowding the pan, add a single layer of the seasoned vegetables. Let them cook for 3-4 minutes without stirring, allowing them to develop a nice char on the bottom.

3. Sauté Until Tender-Crisp: After they have charred, begin to stir and toss the vegetables, cooking for another 4-5 minutes until they are tender but still have a slight crispness. You don’t want them to become mushy.

4. Combine and Finish: Once the first batch is cooked, remove it to a plate and repeat the process with the remaining vegetables. When the final batch is almost done, add all the previously cooked vegetables back into the skillet to heat through together.

5. Add the Finishing Touch: Remove the skillet from the heat. Squeeze the juice of one large lime all over the vegetables and toss to combine. This bright, acidic finish is crucial for waking up all the smoky flavors.

Step 3: Serve

1. Warm the Tortillas: While the vegetables are cooking, warm your tortillas. You can do this by wrapping them in a damp paper towel and microwaving for 30-45 seconds, or by heating them one by one in a dry skillet for about 15-20 seconds per side.

2. Assemble and Enjoy: Serve the sizzling vegetarian fajita skillet immediately with the warm tortillas and a spread of all your favorite toppings.