Preheat your oven to 375 degrees F. Lightly grease a 9x13-inch casserole dish with olive oil or cooking spray. Set aside.
Add the olive oil to a large skillet set over medium-high heat. Add the sliced shallots and cook, stirring often, until tender and starting to turn golden - approximately 5 minutes. Add the garlic and cook, stirring continuously, for 30-60 seconds more.
Add the chopped jalapeño pepper (if using) and spices (the taco seasoning, ground cinnamon, salt, and pepper) to the shallots. Mix well to combine. Cook for approximately 30-60 seconds.
Add the chopped red bell pepper, cherry tomatoes, zucchini, and yellow squash. Mix thoroughly and continue to cook, stirring often, for approximately 6-8 minutes, or until vegetables are just starting to soften. Stir in the chopped cilantro and remove from heat.
To assemble your enchiladas add approximately 1/2 a cup (or more if needed) of enchilada sauce to the bottom of your prepared baking dish and spread evenly to coat the surface. Add approximately 1/2 cup (give or take) of the cooked veggie mixture down the middle of a tortilla and sprinkle with cheese. Roll up as snug as possible and transfer to your baking dish, seam-side-down. Repeat with the remaining tortillas and filling.
Once your baking dish is filled with rolled-up enchiladas, generously drizzle with the remaining enchilada sauce and sprinkle the top with shredded Monterey Jack cheese.
Transfer to your preheated oven and bake for approximately 20 minutes, or until the cheese is golden and bubbly.
Remove from the oven and serve with optional garnishes such as additional cilantro and enchilada sauce, sour cream, or fresh lime juice.