Place the apples, water, ¼ cup cane sugar, apple cider vinegar or lemon juice, and ¼ teaspoon of the spice blend in a heavy-bottomed saucepan.

Bring to a gentle simmer over medium heat. Reduce the heat to medium-low and simmer for about 20 minutes, stirring occasionally, until the apples are very soft. Add a small splash of water if the mixture begins to dry out before the apples soften.

Remove the saucepan from the heat. Using an immersion blender, purée the apples until smooth. Alternatively, use a countertop blender or food processor, following the manufacturer’s instructions for blending hot foods, then return the purée to the saucepan.

Stir in the kosher salt and vanilla. Taste and add up to another ¼ teaspoon of the spice blend, if desired. If your apples are especially tart, add more cane sugar, 1 tablespoon at a time, to suit your taste.

Return the saucepan to low heat and cover with a splatter guard—the apple butter will splatter as it thickens. Leave the lid off so moisture can escape. Simmer gently for about 20 minutes more, stirring frequently and scraping the bottom to prevent sticking.

The apple butter is ready when it mounds softly on a spoon without watery liquid separating around the edges. It will thicken further as it cools.

Transfer to a clean, heat-safe container, cool briefly, and refrigerate promptly.