1 cup fruit juice (pure juice–not a fruit-flavored drink) or nectar, such as Goya, Mott’s, or Kern’s, chilled or at room temperature
1 1/4-ounce package gelatin
Lightly coat 16 tartlet molds or mini-muffin tins with oil.
Place 1/4 cup of the juice in a medium bowl and sprinkle in the gelatin. Let sit for 1 minute.
Meanwhile, in a small pan, bring the remaining juice to a boil. Add it to the gelatin mixture, stirring until the gelatin is dissolved.
Spoon the mixture into the molds. Chill in the refrigerator until set, 2 hours.
Pop the tartlets out. Serve them cold or at room temperature within 2 hours, or store them in an airtight container in the refrigerator for up to 3 days.