Start by finely grating the zucchinis using a grater, creating noodle-like strands that will form the base of your sauce.
Heat a large skillet over medium heat, then add a splash of olive oil. Once shimmering, add the chopped onions and sauté until they become translucent and fragrant, about 5 minutes.
Add the minced garlic to the skillet and cook for about 30 seconds until fragrant, stirring constantly to prevent burning.
Stir in the grated zucchini and cook, stirring occasionally, until the zucchini releases its juices and softens, about 8 minutes. It should look tender and slightly wilted.
Pour in the crushed tomatoes and add a pinch of red pepper flakes, stirring to combine everything evenly.
Bring the sauce to a gentle simmer and add a splash of balsamic vinegar. Let it cook uncovered for about 15 minutes, stirring occasionally until it thickens slightly and the flavors meld.
Taste the sauce and adjust the seasoning if needed—adding more red pepper flakes for heat or more vinegar for brightness.
Once the sauce has thickened to your liking and the zucchini is tender, remove from heat and serve hot, ideally over pasta or as a standalone vegetable dish.
