In a sauce pan of boiling water, cook the Meyer lemon for about 10 seconds. This will soften the skin, which will be used in the recipe. Cut off the ends and discard. Cut the cooked fruit into sections.
In a food processor finely chop the cut up Meyer lemon. Add the 1 1/3 cups of Meyer lemon juice and process until the desired texture. I like mine with some bits of rind and my husband likes his smooth. If you want the pâte to be perfectly smooth you can strain the mixture at this point.
Add the Meyer lemon, sugar and rosemary sprig to a medium sauce pot and bring to a boil. Once it is boiling you will cook the mixture for 5 minutes. Half way through, add the butter and continue to cook. Be sure to stir constantly and make sure it doesn’t boil over. You may have to adjust the temperature as you cook.
Once the mixture has cooked for the full 5 minutes turn off the heat, remove the rosemary sprig and add the Certo. Stir until well combined. Pour into prepared baking dish. Let sit at room temperature until completely set, about 2 hours.
Cut with a sharp knife or cookie cutter and roll in sugar to serve. Can be served cold or at room temperature. Keeps for a few days in the refrigerator.