1 large flank steak — butterflied
1/4 cup red wine vinegar
1 teaspoon garlic, finely chopped
1/2 teaspoon Thyme, dried
1 bunch spinach
2 carrots, peeled and cut lengthwise
2 eggs, hard-cooked and cut lengthwise
1 medium onion, thin sliced and cut into rings
2 tablespoons parsley, finely chopped
1/2 teaspoon red pepper flakes
1 teaspoon sea salt
2 tablespoons vegetable oil
2 to 3 cups beef broth
Place the meat in a glass dish. Mix together the vinegar, garlic and thyme. Pour over the meat and let marinate for 1 or 2 hours at room temperature. Preheat the oven to 375 degrees F.
Wash the spinach under cold running water; drain and trim off the stems. Spread the leaves evenly over the meat. Lay the carrots, in rows, across the grain of the meat. Place the egg quarters between the rows of carrots. Scatter the onion rings over the eggs and carrots, then sprinkle the parsley, red pepper flakes and salt over all. Carefully roll up the meat with the grain, jellyroll fashion. Secure with toothpicks and lace up with string. Or tie with string at 1-inch intervals.
Heat the oil in a dutch oven. Add the meat and brown well on all sides. Add the stock, cover tightly, and bake for 1 hour.
Remove the matambre from the pan to a board and let rest for 10 minutes. Using a sharp knife, remove the strings and cut the roll into 1/4 inch slices. Arrange on a heated platter and moisten with a little of the cooking broth.