Gather all of your ingredients, and plug your slow cooker in.
Add the pureed pumpkin to your slow cooker, followed by the white and brown sugars, cinnamon, nutmeg, cloves, and ginger.
Pour in the apple cider and stir your ingredients together.
Cook in your crockpot on low for 5 to 6 hours, or on high for 2 to 3 hours. If you choose the low setting, you'll want to stir your pumpkin butter every 90 minutes or so. If you need it done faster, plan to stir every 30 minutes.
Once the pumpkin butter thickens and darkens, you're done. Add the lemon juice and stir to distribute.
Spoon your pumpkin butter into canning jars. If you're going to use the pumpkin butter right away, there's no need to seal them, just stick them in the refrigerator.