Wash and stem your cherries. Using a cherry pitter, remove all pits. Cut cherries in half or roughly chop them depending on how chunky you prefer your jam.
In a large, heavy-bottomed pot, combine the pitted cherries, sugar, and lemon juice. Stir gently to coat all cherries with sugar. Let the mixture sit for 15-20 minutes to allow the cherries to release their juices.
Place the pot over medium heat and stir occasionally until the sugar completely dissolves. Once dissolved, increase the heat to medium-high and bring the mixture to a full rolling boil. Add the tablespoon of butter now if using to reduce foaming.
Maintain a steady boil, stirring frequently to prevent sticking or burning. As the mixture reduces, it will become thicker and more glossy, typically taking 25-35 minutes.
Test for doneness by dropping a small spoonful onto a cold plate from the freezer and letting it sit for 30 seconds. Run your finger through it – if it wrinkles and doesn't immediately flow back together, it's ready.
Once the jam reaches the proper consistency, remove from heat. Stir in the vanilla and almond extracts if using.
Ladle hot jam into sterilized jars leaving ¼-inch headspace. For canning, wipe rims, apply lids and bands, and process in a water bath for 10 minutes. For refrigerator jam, simply cool completely before storing.