Step 1

If canning, prepare a water bath canner, jars and lids before beginning. If not canning, no worries, just let it cool on the counter in jars before storing in the refrigerator.

Step 2

Heat oil in a heavy-bottomed pan or Dutch oven over medium-high heat, then add the sliced onions and stir to coat.

Step 3

Reduce the heat to medium and cook the onions for 45-50 minutes, stirring often.

Step 4

Prepare jars and a hot water bath.

Step 5

Add maple sugar to the cooked onions and stir to dissolve the sugar.

Step 6

Increase the heat to medium-high and cook the onions and sugar for 3-4 minutes, stirring constantly.

Step 7

Carefully stir in the vinegar and lemon juice, being cautious of splattering and vinegar vapor.

Step 8

Reduce the heat to medium and add salt to the mixture.

Step 9

Cook the onion mixture until the vinegar has reduced to a sticky syrup, about 10-12 minutes.

Step 10

Pour or ladle the hot jam into prepared hot jars, leaving ½ " headspace at the top of the jars.

Step 11

Wipe the rims of the jars with a clean cloth, and apply the 2-part canning lids.

Step 12

Preserve the homemade onion jam using a hot water bath canning method for 10 minutes, adjusting time if necessary for altitude.

Step 13

After processing, turn off the heat and leave jars in the canner, uncovered, for 5 minutes. Remove the jars from the canner and let them cool for 12-24 hours, then check that the jars have sealed. Refrigerate any unsealed jars.

Step 14

Sealed red onion jam will retain peak quality for up to 18 months stored in a cool, dry place or pantry. Refrigerate the jam once opened.