For the Steak:

• 1 1/2 pounds boneless steak such as ribeye (filet, sirloin)
• Neutral oil (as needed)
• Kosher salt (to taste)
• Freshly cracked black pepper (to taste)

For the Cowboy Butter:

• 1 stick unsalted butter (at room temperature)
• 4 garlic cloves (minced)
• 1/2 lemon (zested and juiced)
• 1 tablespoon dijon mustard
• 1 teaspoon paprika
• 1/2 teaspoon cayenne
• 1/2 teaspoon dried thyme
• 1 teaspoon red pepper flakes
• 1 tablespoon chives (minced)
• 2 tablespoons fresh parsley (minced)
• Kosher salt and pepper (to taste)

Additional Ingredients:

• 3 sweet onions (thinly sliced)
• 9 slider buns
• 3/4 pound sliced havarti cheese