Preheat oven to 400°F (200°C).

Toss beef bones (8 lb) with olive oil (¼ cups) and spread them in a single layer on a roasting pan.

Roast bones for 1-1.5 hours, flipping halfway through, until deeply browned.

Bones should be a rich, dark brown color

Add carrots (2 cups), celery (2 cups), and onion (2 cups) to the roasting pan with the bones. Stir in tomato paste (½ cups).

Continue roasting for another 30 minutes, or until the vegetables are caramelized.

Vegetables should be softened and browned

Transfer the bones and vegetables to a large stockpot.

Deglaze the roasting pan with red wine, scraping up any browned bits from the bottom. Pour the wine into the stockpot.

Use a wooden spoon to scrape the pan thoroughly.

Add beef stock (8 cups), bay leaf (2 leaves), and peppercorns to the stockpot. Bring to a boil, then reduce heat and simmer gently for 6-8 hours, skimming off any foam or impurities that rise to the surface.

Liquid should be simmering gently, not boiling vigorously

Strain the stock through a fine-mesh sieve lined with cheesecloth. Discard the solids.

Return the strained stock to the stockpot and simmer over low heat until reduced by half, about 2-4 hours.

Sauce should be thick enough to coat the back of a spoon • Intensely savory aroma