Preheat oven to 400 degrees.
Set a cast iron skillet over medium heat. Add grapeseed oil.
In a small bowl, mix rosemary, salt, sage, and pepper. Mix to combine.
Pat pork tenderloin dry with a paper towel. Add a spoonful of the mixture on to your cutting board, and place pork tenderloin over spices. Continue pressing herb mixture in to pork tenderloin. Add minced garlic, again pressing in to the tenderloin. Sear pork tenderloin on all sides, transferring to the oven once all sides have been browned. Cook for 15 minutes, or until internal cooking temperature reaches 145 degrees.
Transfer pork to a plate and tent loosely with tin foil.
Set the hot pan over a low flame. Add a small amount of grapeseed oil if there isn't at least 1 teaspoon of drippings in the pan. Add shallot and garlic, sauteeing until fragrant.
Add pumpkin and pinot noir, whisking until combined. Feel free to add water to thin the sauce out if you prefer.
Add the rosemary and the butter, stirring until the butter has melted. Serve with the warm pork tenderloin.