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Roasted Vegetable Sandwich with Avocado-Basil Aioli
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5 from 2 votes

Roasted Vegetable Sandwich with Avocado-Basil Aioli

This vegan, gluten-free, and grain-free roasted vegetable sandwich with avocado-basil aioli is packed to its mushroomy edges with goodness. Portobello "buns" are piled high with roasted veggies and slathered in a delightfully creamy avocado-basil aioli. 
Prep Time20 mins
Cook Time25 mins
Total Time45 mins
Course: Handheld Bites, Sandwich
Cuisine: Gluten-Free, Grain-Free, plant-based, Vegan
Servings: 2 sandwiches


For the Buns

  • 4 large portobello mushroom caps
  • sea salt
  • black pepper

For the Roasted Vegetables

  • 1 vine-ripe tomato, sliced into 1/3-inch-thick rounds
  • 1/2 jar roasted red peppers
  • 1 medium zucchini, ends trimmed, halved, and sliced lengthwise
  • 1 small red onion, peeled and sliced into 1/2-inch-thick rounds
  • 1/2 jar roasted red peppers, sliced into 2-inch strips

For the Avocado-Basil Aioli

  • 1 avocado, pitted
  • 1/3 cup fresh basil leaves
  • 1 tablespoon fresh lemon juice
  • 1 garlic clove, peeled
  • 1/4 teaspoon sea salt or to taste

For Garnishing

  • 4 butter lettuce or romaine leaves, washed and roughly torn


  • Preheat oven to 400F.
  • Clean, de-stem, and scoop out the gills of the portobello mushrooms. Place all four, gill-side-down, on a large baking sheet lined with parchment pepper. Sprinkle with the tops with salt and pepper and roast for 20-25 minutes or until tender.
  • At the same time, add the tomatoes, zucchini, and red onion to a pan lined with parchment paper, and sprinkle with sea salt and black pepper. Bake alongside the mushrooms for 20-25 minutes or until tender, flip halfway through and season other side of veggies with black pepper and sea salt.

For the Avocado-Basil Mayo

  • Add the avocado flesh, basil leaves, garlic, lemon juice, and sea salt to a food processor. Process for 2-3 minutes or until smooth, stopping as needed to scrape down the sides.

To Assemble

  • Slather the gill-side of all 4 mushroom caps with the avocado-basil aioli. On two of the portobello caps, layer the lettuce leaves, zucchini, tomatoes, red onion, and roasted red peppers. Top with the other portobello caps, and serve.