Steak Sandwich with Horseradish Mayo & Tomato - Backyard Farms

Ingredients

• 2 Tbsp. unsalted butter
• 1 medium red onion, thinly sliced
• 1-2 Tbsp. refrigerated prepared horseradish, drained
• 1/2 cup mayonnaise
• 1 Tbsp. sour cream
• 1 large garlic clove, minced
• 1 lb. boneless ribeye steaks
• 1 tsp. each Kosher salt and freshly-ground black pepper
• 1 Tbsp. canola oil
• 8 1" thick sourdough slices, toasted
• 4-8 butter lettuce leaves
• 1 beefsteak tomato, sliced