Prepare the marinadeIn a bowl, whisk together the olive oil, soy sauce, Worcestershire sauce, balsamic vinegar, brown sugar, garlic, black pepper, salt, onion powder, smoked paprika, and rosemary until the sugar is dissolved.
Marinate the venisonPat the venison backstrap dry with paper towels. Place it into the marinade and coat well on all sides. If they fit, you can use your bowl, or just transfer the marinade to a zippered bag.Seal and refrigerate for 4 to 12 hours. (Do not exceed 24 hours — the acid will begin to change the texture.)Remove the meat from the refrigerator about 30 minutes before cooking so it can come closer to room temperature.
Cook the backstrapPreheat oven to 375°FHeat a cast iron skillet over medium-high heat until very hot.Remove the venison from the marinade and lightly pat dry. (Do not rinse.)Add 1 tablespoon of oil to the skillet, then place the backstrap in the pan.Sear for about 1 minute per side, turning to brown all sides evenly. After you rotate to the final side, transfer to the oven on the center rack to bake for 5-15 minutes. *See notes below!Cook until the internal temperature reaches your desired doneness — I did 125–130°F for medium-rare(see notes below).
Rest the meatTransfer to a cutting board and tent loosely with foil.Let rest 10 minutes before slicing.
Slice and serveSlice the venison against the grain into ½ inch medallions and serve immediately.
Notes
Choose your doneness from the list below and cook your backstrap to the associated temperature:
Rare — 120°-125°F
Medium-rare — 125°-130°F
Medium — 130°-140°F
Medium-well — 140°-150°F
Well-done — 150°-160°F+
While many people prefer their backstraps rare, foodsafety.gov recommends cooking venison to an internal temperature of 160°F.
You can leave out the balsamic vinegar and replace it with an equal amount of soy sauce!
Backstraps can vary greatly in size. For a 3" thick backstrap, it takes about 9 minutes in the oven to reach medium rare. Because of this, I highly, highly recommend using an instant digital thermometer, and checking the temp right before it goes in the oven, and then every couple of minutes!
Don't skip resting the meat! It's essential to have juicy and flavorful backstrap.