Portobello Cheeseburger with Sweet Onion Relish

Sink your teeth into the ultimate plant-based delight with this Portobello Cheeseburger with Sweet Onion Relish. Juicy, marinated Portobello mushroom caps are grilled to perfection, topped with melted cheddar, Swiss, or provolone cheese, and paired with a luscious, caramelized sweet onion relish that adds the perfect balance of savory and sweet. Nestled on a toasted bun with crisp lettuce, ripe tomato, and a creamy slather of mayo, this vegetarian burger is a gourmet twist on a classic, bursting with bold flavors and textures. Ready in just 40 minutes, it’s an ideal centerpiece for weeknight meals or summer cookouts. Customize with your favorite toppings and serve alongside crispy fries or a fresh salad for a restaurant-worthy experience straight from your kitchen!

Nutriscore Rating: 66/100

Prep Time:20 mins

Cook Time:20 mins

Total Time:40 mins

Servings: 4

Ingredients

• 4 large caps Portobello mushrooms
• 4 tablespoons Olive oil
• 2 tablespoons Balsamic vinegar
• 2 tablespoons Soy sauce
• 2 cloves, minced Garlic
• 0.5 teaspoons Salt
• 0.5 teaspoons Black pepper
• 4 slices Cheese slices (cheddar, Swiss, or provolone)
• 2 medium, thinly sliced Sweet onions
• 2 tablespoons Butter
• 1 tablespoon Brown sugar
• 4 Burger buns
• 4 large leaves Lettuce leaves
• 1 large, sliced Tomato
• 4 tablespoons Mayonnaise
• 4 teaspoons Ketchup (optional)

Directions

Step 1

Clean the Portobello mushroom caps by gently wiping them with a damp paper towel. Remove the stems, but keep the caps intact.

Step 2

In a large mixing bowl, prepare the marinade by whisking together olive oil, balsamic vinegar, soy sauce, minced garlic, salt, and black pepper.

Step 3

Place the Portobello caps in the bowl, ensuring they are well coated in the marinade. Let them marinate for 15 minutes, flipping them halfway.

Step 4

While the mushrooms marinate, prepare the sweet onion relish. Heat butter in a skillet over medium heat, then add the sliced onions. Cook for 10 minutes, stirring occasionally, until the onions are soft and golden.

Step 5

Add the brown sugar to the onions and cook for another 5 minutes, stirring frequently, until the mixture becomes caramelized. Remove the skillet from heat and set aside.

Step 6

Preheat a grill or skillet over medium-high heat. Place the marinated Portobello mushrooms on the grill, gill side up, and cook for 5 minutes. Flip the mushrooms and cook for another 5 minutes, or until they are tender.

Step 7

During the last 2 minutes of cooking, place a slice of cheese on each mushroom cap to allow it to melt. If desired, lightly toast the burger buns on the grill or in a toaster.

Step 8

Assemble the burgers by spreading mayonnaise (and ketchup if using) on the bottom halves of the buns. Add a lettuce leaf and a slice of tomato to each bun.

Step 9

Place the grilled Portobello mushroom caps with melted cheese on top of the tomatoes. Add a generous spoonful of the sweet onion relish over the mushrooms.

Step 10

Top with the remaining halves of the buns and serve immediately. Pair with your favorite sides like fries or a salad.

Nutrition Facts

Serving size	(1522.4g)

Amount per serving	% Daily Value*
Calories	2480.8

Total Fat 166.8g	0%
Saturated Fat 45.9g	0%
Polyunsaturated Fat 6.2g
Cholesterol 245.8mg	0%
Sodium 6074.6mg	0%
Total Carbohydrate 186.4g	0%
Dietary Fiber 22.7g	0%
Total Sugars 66.9g
Protein 65.6g	0%

Vitamin D 29.9IU	0%
Calcium 1119.4mg	0%
Iron 10.4mg	0%
Potassium 3439.3mg	0%

*The % Daily Value tells you how much a nutrient in a serving of food contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.

Source of Calories

Fat: 59.8%

Protein: 10.5%

Carbs: 29.7%