Preparing vegetables: Slice yellow squash/zucchini lengthwise as thin as possible (after cutting off the head) to mimic the lasagna noodle, then either salt them or sit them on paper towels, like with bacon, to get out all the extra moisture. Dice green bell pepper, chop onion, mince garlic, and set aside.
Meat Sauce: Turn stovetop to medium-low. In a large skillet, add olive oil, ground beef and ground turkey. Combine well. After it starts to brown, add onion powder, garlic powder, oregano, basil, cracked pepper, 2 tbsp water. Mix together thoroughly until meat is almost entirely cooked through. Then add onion, garlic, green pepper, tomato sauce, tomato paste. Mix together fully. Then cover for about 10-15 minutes until completely cooked through. Set aside.
Ricotta Mixture: Combine ricotta cheese, parsley and egg into bowl. Whisk together until completely combined. Set aside.
Pre-heat oven to 350°F.
Assemble the Lasagna: Grease a deep 9x13 baking dish with cold butter. Layer 1: layer in 1/2 the meat sauce until bottom completely covered, keeping it thin and as flat as possible. Layer 2: yellow squash slices, adding them in like puzzle pieces until you've created a layer.Layer 3: 1/2 the ricotta mixtureLayer 4: spinach (continue to push down to flatten the ingredients as you go) Layer 5: sliced mushroomsNote: if you don't have a deep enough dish, you can always combine the spinach and mushrooms (use 1/2 quantities of each) and then make one layer out of it. Layer 6: mozzarellaLayer 7: rest of meat sauceLayer 8: yellow squashLayer 9: rest of ricotta mixtureLayer 10: mozzarellaLayer 11: parmesan
Bake: Cover top with aluminum foil. Bake in oven at 350°F for 45 minutes. Remove dish from oven, raise temperature to 375°F. Then remove foil, completely uncovering dish, and put it back in the oven for another 15 minutes, allowing it to become golden brown on the top. Let it cool for about 10 minutes, then slice, serve, and enjoy!