Preheat your oven To 350 F.
Season the pork tenderloin with sea salt and black pepper on both sides.
Sea salt and freshly ground black pepper to taste, 2 lb. pork tenderloin
Place the pork in a baking dish. Sprinkle garlic over the pork, top with the onion and celery, and pour the wine and water over everything.
2 red onions, 1 stalk celery, 4 garlic cloves, 1 cup of red wine, 1 cup of water
Bake in the oven for 45 to 50 minutes.
When the cooking is done, remove the pork from the dish and add everything else from the baking dish into a saucepan over medium heat.
Bring the sauce to a boil. Slowly whisk in the tapioca starch until it thickens, and season to taste with salt and pepper.
2 tbsp. tapioca starch
Slice the tenderloin, pour the sauce over it, and serve.