Use a carrot peeler to take a thin layer of peel off the blood oranges and lemons. Aim for 2 cups of blood orange peel and 1 cup of lemon peel.

Slice the fruit and remove the seeds. Set aside any pith that comes off the fruit.

Wrap the pith and seeds in cheesecloth and secure tightly.

Use a food processor to break down the oranges and lemons until in small bits.

Place the water, processed fruit, peels, and cheesecloth bundle into a large pot. Let this mixture sit overnight (not refrigerated).

On the second day, bring the fruit mixture to a boil. Cook for 20-30 minutes until tender. Discard the cheesecloth bundle afterward.

Measure the fruit and liquid. For each cup of fruit mixture, add 3/4 - 1 cup sugar.

Bring to a boil again and stir until the sugar dissolves. Continue stirring as it reaches gelling point.

Perform a gel test by placing a tablespoon on a cold plate. If it wrinkles when pushed, it’s ready.

Ladle hot marmalade into prepared jars, leaving 1/4 inch headspace. Can it using a boiling-water canner, or refrigerate if you prefer not to seal.