1. Beat egg whites until soft peaks form. Slowly add sugar and jello powder, beating until stiff and glossy. Add vanilla; mix until incorporated.
2. Preheat oven to 250 degrees Fahrenheit. On a parchment-lined cookie sheet, drop meringue by tablespoonfuls, and spread with the back of a spoon to form even circles.
3. Place in oven and bake one hour. Turn off oven and allow to cool with oven door closed.
4. When cool and hardened, spread half of meringue cookies with a thin layer of jam; top with remaining meringues.