Combine chopped thyme, sugar, salt and pepper in a small bowl.

Rub mixture all over pork.

Place on a rack in a roasting pan.

Cover loosely and refrigerate for 8 hours or overnight.

Preheat the oven to 425F.

Brush off excess brine from pork.

Roast pork, rotating the pan several times to ensure even browning, until browned and an instant-read thermometer inserted into the thickest part reads 150F, about 40 to 50 minutes.

Meanwhile, with a paring knife or peeler, remove peel (outer skin) in strips from 1 orange and from lemon.

Finely dice zest. Peel skin off remaining orange, then peel off and discard white pith from oranges and lemon.

Chop flesh, discarding any seeds.

Combine zest and flesh in a medium saucepan with honey, thyme sprigs and 2 tablespoons water.

Place over medium heat and cook, stirring frequently, until jam is thickened and somewhat smooth but still a little chunky, 20 to 25 minutes.

Discard thyme sprigs.

Place pork on a cutting board and let rest for 10 minutes, then carve into thin slices and transfer to a platter.

Spoon pan juices on top and serve with citrus jam.