Grilled Portobello Sandwich with Caramelized Onions, Pesto Mayo and Balsamic Glaze

Ingredients

• 4 fresh Portobello mushroom caps – you can remove the gills with
• a spoon or leave them
• Olive oil
• 1 large sweet yellow onion – sliced thin into 1/2 moons
• Salt and pepper
• 1/2 cup mayonnaise
• 2-3 tsp fresh or prepared pesto
• 1 red pepper – roasted, peeled, seeded and cut into 1/2 inch strips
• 4 focaccia sandwich rolls
• 4 slices provolone cheese
• 1 cup arugula