Gently pluck 4 cups of bright yellow dandelion petals, avoiding green parts. Rinse thoroughly in cool water for about 10 minutes.

In a large pot, combine the cleaned dandelion petals with 4 cups of freshly boiled water. Cover and let steep at room temperature for 24 hours.

Strain the liquid through a fine mesh sieve or cheesecloth into a bowl or pot, pressing down on the petals.

In the dandelion infusion, stir in 0.5 cups of fresh lemon juice and 2 cups of granulated sugar. Mix until dissolved.

Bring the mixture to a rolling boil over medium-high heat, stirring frequently. Add 1 tablespoon of butter to reduce foam if desired.

Once at a hard boil, boil for 1 minute, then quickly stir in the liquid pectin. Boil for 1 more minute, stirring constantly.

Perform a cold plate test by placing a spoonful on a chilled plate to check if it wrinkles after cooling for 30 seconds.

Ladle the set jelly into sterilized jars, leaving ¼-inch headspace. Wipe rims, seal, and cool at room temperature.