Beef steak 'flank steak'

Prepare the Kamado BONO barbecue for direct cooking, light the charcoal with a tanner, place on a stainless steel grill, and wait for the temperature to rise to 250 degrees.
Close the upper and lower air dampers to keep the temperature even.
Place the meat on the grill and cook for a couple of minutes. from both sides.
Remove from heat, season with salt, pepper and roll for 5 minutes. to the foil to rest.

Prepare the sauce:
Peel the onions and cut into small cubes. In a small pot, add the olive oil for the sauce, heat and add the onions. Bake on low heat, stirring, for about 5 minutes, until soft (do not brown). Then pour in the wine and cook for about 20 minutes.
Mix the flour with the cream.
Strain the onions through a sieve. Pour the liquid back into the pot, place on the fire and pour the whipped cream-flour mixture into it, stirring. Mix very well.
When the sauce has boiled, add a piece of butter to it, stirring. When the sauce thickens, remove from heat, season with salt and ground black pepper. The sauce is served warm, but you can prepare in advance and heat it up a bit before serving it on the table.

INGREDIENTS

0.8kg beef (beef flank steak)
Cubeb pepper

For the sauce:
2 onions
1 tbsp olive oil
400 ml of white wine
2 tbsp. flour
300 ml greasy cream
40 g of cold butter
salts
ground black pepper