Preheat the oven to 400 degrees.
In a saucepan over medium heat, add olive oil and diced onion. Stir occasionally. Cook until onions are translucent.
Add can of diced tomatoes (do not drain) to the onions. Cover and simmer on low until tomatoes start falling apart. Approximately 10-15 minutes.
While tomatoes are simmering, spray a 9x13 pan with non-stick cooking spray.
Take your tortillas and place 3-4 of them between two damp paper towels and microwave until soft (approximately 30-40 seconds). This will help make the tortillas soft enough to roll without ripping.
In each tortilla, fill with chicken and 1 tbsp of cheese. Roll your tortillas up and place in the 9x13 pan.
Return to your sauce. Add salsa, greek yogurt, sugar/stevia, chili powder and salt. Simmer for 1-2 minutes.
Place sauce in a blender and blend until smooth. Immediately pour over enchiladas.
Cover the enchiladas with the remaining cheese.
Bake for 30 minutes, or until the cheese is golden brown.
Remove from oven and enjoy!