Bring oranges, orange juice, lemon juice and sugar to a low boil in a large saucepan over medium to medium-high heat, stirring frequently to combine.
Once it reaches a low boil, reduce heat to medium low and add a pinch of salt and stir. Simmer for about 30 minutes and then add thyme and orange zest.
Continue cooking until the mixture is reduced by about a third. It should be thick and syrupy - be patient as the whole process may take up to an hour. Add a bit more sugar to help it thicken even more.
Once thickened, remove from heat and let cool. Transfer to clean jars and store in the fridge. Will keep for a couple of weeks. To store in freezer, make sure to use freezer-safe canning jars to avoid cracking.
*Nutrition information is a rough estimate. *Recipe (as originally written) yields ~4 cups total.