Filet Mignon Sliders with Garlic Aioli and Caramelized Onions - Rothliving

Ingredients

• 1/2 cup mayonnaise
• 1 1/2 teaspoons prepared horseradish
• 1 garlic clove, minced
• 1/2 lemon, zest, and juice
• Kosher salt
• fresh cracked black pepper
• 2 red onions, thinly sliced
• 1 tablespoon olive oil
• 1 tablespoon sherry vinegar
• 4 tablespoons butter, separated
• 3 garlic cloves, peeled and smashed
• 1 pound center-cut beef tenderloin, sliced into 8 equal portions
• 2 tablespoons vegetable oil
• 8 mini brioche buns
• handful of arugula