In a nonstick pot, over medium heat, stir together water, brown sugar, and white sugar.
Bring to a simmer and stir in cream of tartar and salt.
Bring to a very light boil and cook for about 8 minutes or until coats the back of the spoon. Stirring frequently. (Be careful not to burn the mixture. Reduce heat if needed.)
Once thickened, remove from heat and stir in butter.
Once butter has melted stir in vanilla extract and maple extract.
Pour syrup into a serving dish.
Let syrup cool slightly, which will allow it to thicken up even more.
Store in the fridge. (syrup will solidify, microwave to reheat)