Portobello Burger

Ingredients

• 3 tablespoons olive oil
• 1 1/2 tablespoons balsamic vinegar
• 1 teaspoon dried basil
• 1 teaspoon dried parsley
• 1 teaspoon dried thyme
• Pinch of kosher salt
• Pinch of freshly ground black pepper
• 6 portobello mushrooms, cleaned
• 6 brioche or gluten-free buns, sliced in half
• 6 slices beefsteak tomato
• 6 slices red onion
• Butter lettuce leaves, for serving
• Suggested toppings: mustard, mayonnaise and ketchup