Preheat oven to 250 degrees Fahrenheit (120 degrees Celsius).

Combine apples, three of the apple cores, apple juice, sugar, and salt in a mediumsized pot. Bring to a boil, then lower to a simmer. Partially cover and cook until apples are soft, about 20 minutes.

Remove from heat. Add the lemon juice, cinnamon, vanilla, and cloves. Let steep for a while. (This can be done a day in advance and refrigerated until the next step.)

Remove two apple cores from the mixture and pour the mixture into a medium-sized Pyrex dish sprayed with cooking spray. Bake for two and a quarter to two and a half hours, uncovered, until thickened and deep amber in color, stirring every 30 minutes.

After one hour of baking, remove the pan from the oven. Remove the last apple core and blend the mixture with an immersion blender until creamy. (Be careful, as the mixture is hot.) Return to the oven and continue baking.

Cool completely before refrigerating. This lasts in the fridge for about five days. Can be frozen too.