Poach the chicken breast in water or chicken stock for 10 minutes.
Cool and cut into cubes.
Place the tomato and chili powder in a blender and blend until is forms a smooth puree.
Heat 1 tablespoon (15 ml) of the butter in a skillet and cook the puree over moderate heat for about 5 minutes, stirring frequently.
Add the chicken cubes and season to taste with salt and pepper.
Beat the eggs with salt and pepper to taste.
Heat the remaining tablespoon of butter in an omelet pan over high heat until the butter foams.
Pour in the beaten eggs and stir rapidly with the back of a fork until the eggs are cooked but still soft and moist.
Add the chicken mixture and tip the pan to roll the omelet over the filling, using the fork to assist.
Roll out of the pan onto a warm serving platter.