Wash the apples well. Core them and cut in 1-inch slices. Put them in the liner of the crock pot.

In a medium bowl, whisk together the brown sugar, spices, and salt until well combined.

Add the brown sugar mixture and vanilla to the apples and toss until they’re well coated.

Put the lid on the crock pot and cook on Low, stirring occasionally, for 10 hours. The apples will start to break down as they cook.

Unplug the slow cooker. Use an immersion blender to puree the apple mixture. Be careful, starting on the very lowest speed and gradually increasing speed if needed. Puree until mixture is very smooth, about 5 minutes.

Fill your canning pot half full with water, put it on the burner, and turned the heat to High.

Ladle the hot apple butter into the sterilized jars, filling to within ⅛ inch of tops.

Wipe the jar rims and threads with a clean damp cloth. Cover with the two-piece lids and screw the bands on tightly.

Arrange the upright jars on the rack in the pot. Make sure the water can flow freely between each jar.

Put the lid on the pot and bring the water to a full boil. Now you’ll start timing to process the apple butter. If you’re at sea level, process the apple butter for 5 minutes. (IMPORTANT: If you're at an elevation higher than 1,000 feet you'll need to adjust the cooking time. See the Notes below for exact timing.) Then turn off the heat and leave the jars in the water for an additional 5 minutes to help stabilize the temperature.

Remove the jars and transfer to a wire rack to cool completely to room temperature. Next, press in the middle of each lid to check the seals. The lids shouldn’t ‘give,’ and should feel tight. Store the jars in a cool, dark place. Makes about 8 cups, or 8 8-ounce jars.