Divide the cheese mixture into six 6-ounce jars. Place the jars in a baking pan and add boiling water to the pan until it’s about halfway up the jars, to create a water bath. Cover and bake in the water bath for about 25 minutes, or until just set. Remove from oven and allow to cool while you make the sauce.
To make the roasted tomato and feta sauce: Raise the oven to 450°F.
Place the feta in the middle of a baking dish. Scatter the cherry tomatoes, chopped shallot, smashed garlic cloves, garlic powder, thyme, and red pepper flakes around the feta. Drizzle with the olive oil. Drizzle the balsamic over the feta. Bake until the tomatoes start to break down and the cheese just starts to brown, about 15 minutes.