Start by washing your medium-sized zucchini and yellow summer squash. Cut them into 1-inch rounds or chunks for even cooking. Slice the red onion into thick wedges.

Pat the sliced vegetables aggressively with a clean kitchen towel to remove excess moisture.

Preheat your cast-iron grill pan over medium-high heat for at least five minutes until hot.

Once the grill pan is hot, add a tablespoon of high-smoke point oil and swirl to coat.

Place the zucchini, yellow summer squash, and red onion in the pan in a single layer. Let cook for about four minutes.

Use tongs to gently turn the vegetables after four minutes and cook for an additional three minutes.

Remove from heat and drizzle with balsamic glaze. Sprinkle with kosher salt, cracked black pepper, and freshly chopped parsley.