In a non-stick pan over medium heat, add the oil, sauté the chicken sausage until browned, then add in the tomatoes and eggs.
After the egg begins to set around edges, carefully lift the egg from the side using a heat-safe spatula, and tilt the pan so the uncooked egg can reach the bottom of the pan. Repeat this process, tilting as necessary until the egg is no longer runny.
Add the cheese; fold the omelet in half using the spatula, turn down the heat to low and allow the cheese to melt.
Lightly toast the bread.
Place the eggs on the bread, cut in half and serve with sliced apple.