Heat oven to 350°F. Grease 9-inch square pan. In large bowl, beat eggs until light and fluffy. Add brown sugar, beat well. Add vanilla, hazelnuts, dates and pineapple; mix well.
Lightly spoon flour into measuring cup; level off. Stir in flour and baking powder; mix well. Spread mixture in greased pan.
Bake at 350°F. for 25 to 35 minutes or until edges are golden brown and center is set. Cool 15 minutes. Cut into bars. Cool 15 minutes or until cooled completely.