Step 1: Prepare the Citrus Fruits

• Wash the oranges and lemons thoroughly. Slice them in half lengthwise, then thinly slice each half, including the peel. Remove any seeds as you slice.

Step 2: Combine Fruits and Water

• In a large, heavy-bottomed pot, combine the sliced oranges, lemons, and water. Bring the mixture to a boil over high heat. Reduce the heat to low and simmer uncovered for 1 hour, stirring occasionally.

Step 3: Add the Sugar

• After the fruits have softened, add the sugar to the pot and stir well to dissolve. Increase the heat and bring the mixture to a full boil.

Step 4: Cook the Marmalade

• Boil the mixture rapidly for about 15-20 minutes, stirring frequently to prevent sticking. Use a candy thermometer to check when the temperature reaches 220°F (104°C), which indicates the marmalade is ready.

Step 5: Test for Set Point

• To check if the marmalade is set, place a small spoonful on a chilled plate and let it cool for a minute. If it forms a gel-like consistency, it’s done.

Step 6: Jar the Marmalade

• Remove the pot from heat and skim off any foam. Pour the hot marmalade into sterilized jars, leaving 1/4 inch of headspace. Seal the jars tightly and allow them to cool completely.