Thinly slice the flank steak against the grain into bite-sized strips.
In a small bowl, combine the sea salt, black pepper, ground cumin, and garlic powder, then toss with the steak strips to coat evenly.
Heat the avocado oil in a cast-iron skillet over medium-high heat until shimmering.
Add the steak to the skillet and sear for 2-3 minutes until a deep brown crust forms; remove the steak from the pan and set aside to rest.
In the same skillet, add the sliced bell peppers and red onion, sautéing for 3-4 minutes until they are tender-crisp and slightly charred.
Wipe the skillet clean and place the sprouted grain tortilla in the center over medium heat.
Sprinkle the shredded cheddar cheese over one half of the tortilla, then layer on the seared steak and sautéed vegetables.
Fold the tortilla in half and press down firmly with a spatula, toasting for 2 minutes per side until the cheese is fully melted and the exterior is golden brown.
Remove from heat, let sit for one minute, then slice into wedges and serve immediately.