Yummy Steak Salad

Ingredients

• 2 (8-12-ounce) rib-eye or striploin steaks, 1-inch-thick
• 1 tablespoon olive oil
• salt, to taste
• black pepper, to taste
• 1 tablespoon salted butter
• 1/2 cup mayonnaise
• 1/4 cup sour cream
• 1 tablespoon white wine vinegar
• 2 tablespoons fresh parsley, chopped
• 1 teaspoon Dijon mustard
• 1 clove garlic, minced
• 1/2 teaspoon onion powder
• 1 heart romaine, chopped
• 2 cups arugula
• 1/2 cup red onions, thinly sliced
• 2 cups cherry tomatoes, halved
• 1 avocado, thinly sliced
• 1/2 cup blue cheese or feta cheese, crumbled