Start by cutting the oranges into small pieces and if they have any seeds, remove them. Cut all the oranges the same way and place them in a large mixing bowl. We’ll also need one whole lemon with the peel. Cut the lemon into slices, remove the seeds and cut into small pieces.
Add the lemon to the mixing bowl with the prepared oranges and toss them all together with a hand mixer. You can also use a food processor or a blender to get the same result.
Next step is to weight our prepared orange mixture in order to figure out how much sugar we need to add. I have 1027 grams of orange mixture, so I will take the same amount of sugar. I really like this way of making jam because it doesn’t matter how many oranges you start with.
Place the pan on the heat and bring it to a boil. Then reduce the heat to low and cook the jam for about an hour, stirring occasionally. During the cooking process bubbly foam will form which must be carefully removed with a spoon. Also, the thicker the jam becomes, the more often it needs to be stirred.
Pour the hot jam into prepared canning jars. Place the lid and screw bands tightly. Turn the jars upside down, so the lids are at the bottom, until they cool completely.