1.
Pierce each steak several times with carving fork, season with salt & pepper; place in shallow bowl.
2.
Add 1/3 cup olive oil, and 1/3 cup red wine vinegar, rosemary and garlic. Marinate steaks 30-45 minutes, turning several times.
3.
Heat 2-3 Tbsp. olive oil in heavy skillet and cook steaks until brown and crusty (1-2 minutes each side). Remove steaks.
4.
Now using the hot skillet, add 1 Tbsp. olive oil and sauté the shallots until tender. Add the remaining 1/3 cup vinegar and cook over medium-high heat, scraping all the brown crusty pieces from the pan. Cook glaze until liquid is reduced by half and stir in butter.
5.
Slice each steak and drizzle with glaze before serving.