Cook the onions. Heat 2 tablespoons of extra virgin olive oil over medium heat until shimmering but not smoking. Add sweet onions and cook for about 4 minutes until translucent. To add color, raise the heat to medium-high while continuously stirring the onions.
Add the vegetables: Add garlic, yellow squash, and red bell peppers. Drizzle a little more extra virgin olive oil, about 1 tablespoon.
Season and cook: Season with salt, pepper, za'atar, Aleppo pepper, and cumin. Stir with a spoon to make sure the vegetables are well coated with the spices. Cook on medium-high, stirring occasionally, until squash and peppers are nice and tender (I like my squash to have some carmelized parts, which is why I cook it over medium-high; you can go with medium if you don't like the carmeliztiaon.
Serve: Transfer to a serving platter. Drizzle with extra virgin olive oil and a generous pinch of za'atar. If you like, add a sprinkle of crumbled feta cheese, pitted olives, and a handful of chopped fresh herbs like parsley. Enjoy!
Notes
Cook's Tip: Cooking time will vary depending on how tender you like your squash. Personally, I like to get a little caramalization/char on my yellow squash, so, I turn up the heat for a short while to accomplish that while maintaining some bite to the squash.
Recipe Variations: This is a super forgiving recipe and is meant to be tailored to your taste. You can mix things up and use a combination of yellow squash and zucchini. Or try a different combination of spices. For example, go the Italian route with a little dried oregano and fresh thyme.