1. In a large saucepan, combine Mountain Dew and lemon juice.
2. Sprinkle pectin over the liquid and whisk to combine.
3. Bring mixture to a full rolling boil over medium-high heat, stirring constantly. Boil for 1 minute.
4. Stir in butter.
5. Add all of the sugar at once and stir until completely dissolved.
6. Return to a full rolling boil and boil for 1 minute, stirring constantly.
7. Remove from heat and skim off any foam.
8. Ladle hot jelly into sterilized jars, leaving 1/4 inch headspace.
9. Wipe rims, apply lids, and process in a boiling water bath for 10 minutes.
10. Remove jars and allow to cool completely.

Notes

1. Measure sugar ahead of time for best results.
2. Stir constantly to prevent scorching.
3. Skim foam for a clearer jelly.

Storage

1. Store sealed jars in a cool, dark place for up to 1 year.
2. Refrigerate after opening and use within 3 weeks.