Pat tenderloin dry. Rub with celery salt and pepper.
Step2
Cook bacon over moderate heat in a heavy kettle, stirring occasionally, until crisp. Transfer, using a slotted spoon, to a small bowl.
Step3
Pour off all but 1 tbsp. bacon fat.
Step4
Increase heat to medium-high and brown tenderloin on all sides. This should take about 5 minutes.
Step5
Transfer tenderloin to a plate and set aside.
Step6
Add wine, bacon and rosemary to kettle and boil 1 minute.
Step7
Put tenderloin back in the kettle and cook, just barely simmering, covered, for 25 minutes. Turn occasionally. An instant-read thermometer inserted 2 inches into the center of the meat should read 125 degrees F for medium-rare.
Step8
Transfer tenderloin to a cutting board and let stand 10 minutes.
Step9
While tenderloin rests, discard bacon from cooking liquid. Add bell pepper and demiglace. Boil over medium heat until reduced to 1 1/3 cups.
Step10
Cut tenderloin into 1/4-inch slices and arrange on a serving platter. Spoon some sauce over the meat and garnish with rosemary sprigs. Serve remaining sauce on the side.
Tips & Warnings
Beef or veal demiglace is available at some supermarkets or in gourmet food stores.