1. Beat egg whites until very stiff.
2. Gradually beat in Sugar; continue beating until glossy.
3. Add lemon juice.
4. Reserve 3 tbsp. of mixture; into the remainder, fold ground hazelnuts.
5. Drop heaping tsp. on prepared baking sheet.
6. Put a small dab of reserved mixture on each and press in a hazelnut in the middle.
7. Bake at 325 degrees for 20 minutes.