Add a teaspoon of baking soda to water and wash the oranges in the baking soda water. Pat dry with a clean kitchen towel.

Cut the oranges in half and remove the seeds using a sharp fruit knife.

Squeeze out the juice using a citrus juicer and scoop out the pulp in a separate bowl, discarding the white pith, seeds, or transparent skin. The total should equal 500 grams (300 ml Juice + 200 grams Pulp).

Remove the white pith inside the rind and julienne the orange rind or cut it into thin strips (60 grams).

Mix sugar and lemon juice with the fruit mixture and set aside for 15 minutes to dissolve the sugar.

Cook the marmalade in a heavy-duty saucepan over low heat, stirring regularly.

After 20 minutes, once the white foam disappears and the marmalade thickens, check the consistency by spreading a spoonful on a plate—it should be sticky.

Allow to cool completely at room temperature and store in a sterilized glass jar with a tight lid.