Grilled Vegetable Antipasto with Red Onion Vinaigrette

INGREDIENTS

• 2 small Japanese eggplant
• 1 small zucchini
• 1 small yellow squash
• 1 small red bell pepper
• 1 small yellow bell pepper
• 2 large portobello mushrooms
• 2 red onions
• 1/4 cup extra-virgin olive oil
• 2 tsp. chopped fresh thyme
• Sea salt and freshly ground pepper, to taste
• Vegetable oil for grill rack
• 2 red onion slices, each 1/2 inch thick
• 3 Tbs. red wine vinegar
• 1/2 tsp. kosher salt, plus more, to taste
• 1/4 tsp. sugar
• Freshly ground pepper, to taste
• 1/4 cup extra-virgin olive oil, plus more as needed