In a small bowl, combine the softened butter with minced garlic and chopped dill. Mix until creamy. Set aside.

Freeze the ribeye steak for about 15 minutes, then slice thinly against the grain. Season with salt.

Heat a skillet over high heat, add oil, and cook the steak strips for 2-3 minutes until golden brown. Remove and set aside.

In the same skillet, add the sliced onions and reduce heat to medium. Sauté until golden brown for about 5-7 minutes, then remove.

Slice the baguette and spread garlic herb butter on both sides. Layer the cooked steak, onions, and havarti cheese.

Preheat the broiler and place the sandwich on a baking sheet. Broil for 2 minutes until cheese is melted and bubbling.

Remove from oven, let sit for a minute, then slice and serve warm.