Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
Slice the chicken breast into thin cutlets and pat them dry with a paper towel.
In a shallow bowl, whisk together the almond flour, garlic powder, dried oregano, sea salt, and black pepper.
Dredge each chicken cutlet in the almond flour mixture until evenly coated, then place them on one side of the prepared sheet pan.
On the other side of the pan, toss the sliced bell peppers and red onion with the olive oil and a pinch of salt.
Bake for 15 minutes, or until the chicken is golden and the vegetables begin to soften.
Remove the pan from the oven and spoon the marinara sauce over each chicken cutlet, followed by the mozzarella and parmesan cheeses.
Return the pan to the oven and bake for an additional 5-7 minutes until the cheese is melted and bubbly and the chicken is cooked through.
Garnish with fresh torn basil before serving hot.