In a saucepan combine lime juice, cherries, and sugar on medium to medium-high heat and bring to a boil for 2 minutes

strain mixture through a fine strainer and press down on the cherries until only the skin is left in the strainer

whisk egg yolks and slowly add the cherry mixture to it whisking continually until all incorporated, return mixture to heat and melt in the butter while whisking until it thickens (coats back of a spoon)

remove from heat and let cool