In a small bowl combine the chili powder, cumin and red pepper flakes.
Heat the olive oil and minced garlic on medium heat in a large pan.
Season the pepper and onions in the pan and saute for 15-20 minutes until tender. Remove from the pan and set aside.
Add a little bit more minced garlic and olive oil to the pan and add in the steak. Season with the fajita mixture and cook through about 20-25 minutes. Toss in the peppers and onions back into the pan at about 20 minutes.
Remove from heat and serve with low carb flour tortillas, or riced cauliflower if eating strict keto.
Serve Keto Steak Fajitas with sour cream, salsa and shredded cheese garnish.