Portobello Burgers with Avocado Mayonnaise

Preheat a grill or grill pan to medium-high heat (about 400°F). Remove the gills from the portobello mushroom caps using a spoon and lightly coat all surfaces with garlic flavor cooking spray.

Arrange the red bell pepper halves and purple onion slices on the grill, skin-side down for the peppers. Cook for 4–5 minutes until grill marks appear and the peppers begin to soften.

Flip the peppers and onions, and continue cooking for another 3–4 minutes until the peppers are tender and charred.

Transfer the roasted peppers and onions to a cutting board. Once cool enough to handle, slice the peppers into strips and roughly chop the caramelized onions.

Place the prepared portobello caps on the grill, stem-side down. Grill for 4–5 minutes until tender and marked, then flip and grill the other side for another 3–4 minutes.

While the mushrooms cook, combine the peeled and sliced California avocados with a fork in a small bowl, mashing until you reach a chunky but spreadable consistency. Season with salt and pepper to taste.

Lightly toast the hamburger buns on the grill for 1–2 minutes until warm and lightly crisped.

Spread the avocado mixture evenly on the bottom half of each toasted bun. Layer a grilled portobello cap on top, followed by the roasted peppers and caramelized onions.

Top with the upper bun half and serve immediately while the mushrooms are still warm.