Preheat the oven to 200°F. (If making multiple omelets, keep the cooked omelets in the oven on a baking sheet until all are complete.)
In a non-stick pan, heat olive oil over medium heat. Sauté spinach until wilted, then add in the tomatoes and egg.
After egg mixture begins to set around edges (about 30 seconds), carefully lift the egg from the side with a heat-safe spatula and tilt the skillet. This allows uncooked egg to reach bottom of skillet. Repeat this process, tilting as necessary.
In a non-stick pan over medium heat, brown the chicken sausage on both sides. Then toast the bread.
Add the cheese and fold the omelet in half with a spatula so that the cheese can melt.
Portion and serve with toast, chicken sausage, and apples.