Preheat immersion circulator, Sous Vide machine, or other Sous Vide set up to reach 140°F.
Take your Loin and generously cover with Salt, Pepper, and Cumin Seed. Thinly slice cloves of garlic and place on the loin.
Place in bag and vacuum seal or remove the air via the water displacement method.
Place the bag in your water bath and set a timer for 2 hours. The time you need to cook the loin depends on its thickness.
After the timer goes off, take the loin out of the bag, and pat dry with a paper towel.
Heat up your cast-iron (or any pan) until it has an opportunity to get nice and hot, then add the fat of your choice, (a medium-high heat fat is always a good idea). Butter can be used instead if you are cautious.
Sear all the edges of the venison loin for about 30 seconds a side until golden brown. Times will vary depending on the heat of cooking fat.
Season with salt and pepper, and slice into medallions