In saucepan on the stovetop add olive oil to pan and cook onions until softened on medium high (about 5-7 minutes)
Once softened add in quartered tomatoes and water. Bring to a boil and simmer on medium heat for 20 minutes.
While sauce simmers slice zucchini and yellow squash thin. (TIP: I love using a mandolin for this step).
Using an 11 x 7 casserole dish layer the zuchini and suqash by alterniating between the two. Make sure when you set them in the pan they are side up. This way your dish will have room for the sauce when you add it.
Once all your squash is layered you will have a beautiful beginning to your dish. (Now is the perfect time to take some insta worthy pics and show off all your efforts)
Remove your sauce from the stove and mash with a fork or blend in a blender.
Top your zucchini and yellow squash with the sauce and cover with foil.
Bake in the oven covered for 20 minutes, then uncovered for 20 minutes.
When you are ready to serve the dish, rinse your microgreens and toss with some olive oil, salt and pepper. Top off the ratatouille with your microgreen salad and serve.