Uncle D's Green Tomato Relish

Submerge canning jars into boiling water for at least 5 minutes to ensure they are properly sterilized. Clean unused lids and rings by gently scrubbing them in warm, soapy water.

Combine vinegar, sugar, salt, mustard seeds, and basil in a large saucepan; bring the mixture to a rolling boil. Reduce heat and continue simmering until sugar has dissolved, approximately 5 minutes. Introduce green tomatoes, bell peppers, onion, and apples into the vinegar mixture; boil the vegetables vigorously, stirring occasionally, until they have softened and blended with the relish flavors, 15 to 20 minutes.

Fill hot, sterilized jars with the relish mixture, leaving about 1/4 inch of space at the top. Use a knife or thin spatula to remove any air bubbles that may have formed inside the jars. Wipe the rims of the jars with a damp paper towel to remove any food residue. Secure the lids and screw on the rings.

Position a rack in the bottom of a large stockpot and fill it halfway with water. Bring the water to a boil, then carefully lower the jars into the boiling water using a jar holder. Leave about 2 inches of space between each jar. If necessary, add more boiling water to bring the water level up to at least 1 inch above the tops of the jars. Continue boiling and cover the pot, then process for approximately 10 minutes.

Remove the jars from the stockpot and place them on a cloth-covered or wooden surface, several inches apart, until they have cooled down. Once cool, press the top of each lid with your finger to ensure a tight seal; the lid should not move up or down at all. Store the sealed jars in a cool, dark area.