Place butter and shallots into a saucepan with salt and pepper; cook and stir shallots over medium-low heat until caramelized and browned, about 20 minutes. Stir occasionally. Add red wine and lemon juice and bring to a simmer.
Reduce heat to low; cook until wine is nearly evaporated and pan juices are thick. Watch carefully, mixture burns easily. Add beef gravy and parsley , return to a simmer, and cook until reduced by half and sauce is slightly thickened, about 10 minutes.
Pour sauce through a fine mesh strainer set over a container. Tap the strainer with a spoon while straining and squeeze out the last remaining drops of sauce from the residue. Season sauce to taste with salt and black pepper.