Sprinkle the fillets with salt and pepper, drizzle with olive oil, and leave for a while.
Heat 2 tbsp oil in a small saucepan. Add onions or garlic and the bulgur and fry gently for 3-4 minutes. Add stock, as much as water is indicated in the description on the package. Bring to cook and stir well. Cover, turn off the heat, and let the bulgur absorb the stock for another 10 minutes.
Bake bell pepper and beetroot on a baking sheet in the oven.
Let the bulgur cool slightly and mix lukewarm with the beetroot and pepper. Season with lime juice, fresh coriander, and mint.
Heat a grill pan and grill the chicken breasts on high heat for 2 minutes on each side. Cover them and let them rest briefly.