Clean all exterior fat, internal vascular structure and silver skin from the heart. After cleaning the heart you should have about 1 pound of clean, red muscle. The meat should look similar in color and texture to beef tenderloin.
Combine the orange juice, wine, olive oil, vinegar, 2 teaspoons salt, 1 teaspoon pepper, chili flakes, thyme and garlic in a container with a cover. Separation is natural. Marinate the heart, covered, in the refrigerator for 2 hours.
Remove the heart from the marinade and pat dry. Sprinkle with salt and pepper. Warm a pan with the extra-virgin olive oil to high heat. When the pan is very hot, sear the heart 1 to 2 minutes per side. Be careful not to overcook, serve rare to mid-rare. Remove from the heat and let rest for 1 minute. Slice thin and serve with some Marrow Butter over Roasted Broccoli and Anchovy.
In a medium mixing bowl, combine the butter, anchovy brine, parsley, tarragon, marrow, lemon zest and salt. Spoon the mixture onto parchment paper and roll into a tight log. Chill for 2 hours. Slice to serve. Leftover butter may be refrigerated and tightly wrapped for up to 1 week.
Preheat the oven to 350 degrees F.
Bring a pot of salted water to a boil. Have an ice water bath on hand. Blanch the broccoli for 30 seconds, then immediately shock in the ice bath. Strain and pat the broccoli dry. Season and toss with olive oil, lemon juice and anchovies. Roast for 15 minutes. Serve immediately.