• 1 (2½- to 3-lb) boneless pork loin roast, trimmed
• ¼ cup dry white wine
• 3 teaspoons juniper berries, lightly smashed
• 7 large shallots, peeled and quartered
• 2 celery stalks, sliced crosswise into ¼-inch pieces
• 1 tablespoon extra-virgin olive oil
• Salt
• Freshly ground black pepper
• 1 large pink grapefruit
• 2 tablespoons gin

Combine pork, wine and half of the juniper berries in a sealable plastic bag; seal bag, pressing out air. Turn bag to coat pork, then put bag in a shallow bowl and marinate, chilled, turning bag over occasionally, at least 4 hours. Bring pork to room temperature, about 1 hour, before cooking. Put oven rack in middle position and heat oven to 350°.

Pat pork dry (discard marinade) and remove any strings, then transfer to a roasting pan. Scatter shallots, celery and remaining juniper berries around pork, drizzle with oil and season with salt and pepper. Bake, basting once halfway through, until meat thermometer inserted into pork registers 150°, about 1¼ hours.

Meanwhile, using a sharp paring knife, cut peel and white pith from grapefruit, then cut each section of fruit away from membranes, cutting as close to membranes as you can, and place sections in a bowl.

Remove pork from oven and let stand in pan 15 minutes. Transfer roast to a cutting board with a lip and let rest, uncovered, for 10 minutes. Add gin to roasting pan, place pan over high heat, and cook for 1 minute, scraping up bits. Remove pan from heat, add grapefruit sections and stir sauce to combine. Slice pork. Divide sauce and pork among serving plates; serve warm.