Rinse 2 cups of fresh raspberries under cold water until clean. Crush gently in a large mixing bowl to release juices.

Remove seeds from 1-2 jalapeños (if preferred). Slice lengthwise and chop finely to yield 1/2 cup.

In a medium saucepan, combine crushed raspberries, chopped jalapeños, 1/4 cup lime juice, 3 cups sugar, and 1 tablespoon butter. Stir over medium heat until blended, about 5 minutes.

Increase heat to medium-high and bring to a rolling boil, stirring continuously for 10 minutes.

Add 1.5 ounces of liquid fruit pectin and stir constantly for 1 additional minute. Remove from heat and skim any foam off the top.

Pour hot jam into sterilized jars, leaving about 1/8 inch of headspace. Wipe rims for a tight seal.

Process the jars in a boiling water canner for 10 minutes to ensure sealing.

Remove jars from boiling water and place upright on a clean towel. Cool for 12-24 hours and check seals.