Wash and trim the rhubarb stalks, discarding toxic leaves. Cut into ½-inch pieces.

Combine rhubarb with crushed pineapple and juice in a large pot, add sugar and let it sit for 2-3 minutes.

Heat mixture over medium-high until boiling, stirring frequently, for about 20 minutes until thickened.

Add lemon juice 5 minutes before cooking time is up and stir.

Remove from heat and stir in the strawberry gelatin until fully dissolved.

Pour hot jam into sterilized jars, leaving ¼-inch headspace, then let cool.

Refrigerate jam for at least 4 hours to set properly.