Translucent Pineapple-Apple Jam with Orange Zest

In a pot, combine pineapple, apple, sugar, orange juice, and lemon zest. Bring to a boil, then reduce heat to medium and cook, stirring frequently, until the pineapple turns translucent (1 to 1 ½ hours).

Place several small plates in the freezer for testing jam consistency later.

Inspect and sterilize 2 to 3 Mason jars by boiling them for 10 minutes and keeping them in hot water. Wash new, unused lids and rings with warm soapy water.

Add a tablespoon of marmalade to a frozen plate. Freeze for 1 minute, then nudge the marmalade with your finger. If it stays nudged, the jam is ready for canning; if not, continue cooking and check every minute.

Pack hot marmalade into sterilized jars, leaving 0.5 to 1.27 cm of space from the top. Run a clean knife or spatula around the jars' insides to remove air bubbles and wipe rims with a moist paper towel.

Place a rack in a large stockpot, fill it halfway with water, and bring to a boil. Lower jars 2 inches apart into the boiling water using a holder and add more water to cover jars by at least 1 inch. Bring to a rolling boil, cover, and process for 10 minutes.

Remove jars from the stockpot and let them rest, several inches apart, for 12 to 24 hours. Press the center of each lid to ensure it doesn't move. Remove rings for storage.