Rub the leg with salt and pepper then sprinkle over the sliced onion and diced garlic. Add the thyme too. Some like to pierce holes into the meat and stick herbs into there, others just make some deep cuts.
Pour some water underneath then place into the middle rack of a 360°F / 180°C preheated oven for 60 minutes. Spoon on some liquid from the bottom of the pan 2 -3 times.
After about 70 minutes, the legs should be ready to be consumed as it's internal temperature should reach 145°F / 63°C but we can roast it more to develop more mature flavors. Optionally we can add a bit of red wine to it too.