Pork Tenderloin with Onions

My brother is visiting for a week, which means I have a sous chef! We both really enjoy cooking, so we're entertaining ourselves by trying out some new recipes together. In light of these activities (and the fact that having company doesn't leave a whole lot of time for creative blogging thought), I'll try to post a few recipes this week. This pork tenderloin recipe is one I've been meaning to post for months; it's a delicious favorite of ours.

Pork Tenderloin with Onions (serves 4-6)

3 tbsp melted butter, divided*
1 tbsp olive oil
3 garlic cloves, minced (or crushed through a garlic press)
1 1/2 tsp dried thyme
salt & pepper
2 small red onions, cut lengthwise into 1/2" slices (2 cups)
2 pork tenderloins (about 1 lb each)
2 tsp flour
1/4 cup light-colored, flavorful liquid (I use anything from chicken broth to white wine, depending on what I have on hand; I've even used Marsala)
3/4 cup water

Preheat oven to 450F. In a small bowl, stir together 1 tbsp butter, oil, garlic, thyme, 1 tsp salt & 1/4 tsp pepper. In a roasting pan, toss onions w/ half the butter mixture; push to sides, place pork in center. Rub remaining butter mixture over pork. Roast 20** minutes. Heat broiler; set rack 4" from heat. Broil 10 minutes, or until pork registers 155F on an instant-read thermometer. Remove pork from pan. Whisk flour & 2 tbsp butter in a small bowl; set aside. Place roasting pan w/ onions on stove over medium-high heat. Add water; bring to a boil, stirring to deglaze the pan. Add broth/wine & flour mixture. Cook sauce, stirring, until slightly thickened, 3-5 minutes. Slice pork, and spoon sauce on top.

*I've substituted olive oil for all of the butter, and that works just fine.
**The original recipe only called for 10 minutes, but I found I needed to double the time for my oven.