Preheat the oven to 325° F and line an 8-inch square baking pan with parchment paper.
Melt the butter in a small saucepan over low heat. Once melted, remove from the heat, and add half of the white chocolate chips. Let stand, and do not stir.
Beat the eggs in a mixing bowl until foamy. Gradually add the sugar, beating at high speed until lemon colored.
Stir in the butter-chip mixture to the eggs. Then add the flour, salt, vanilla extract, lemon extract, and lemon zest. Beat on low speed just until combined.
Spread half of the batter in the prepared baking pan. Bake uncovered in the oven for 15-20 minutes or until golden brown and the top feels firm. It will continue to bake in the next step, so don't overbake it.
Stir the remaining white chocolate chips into the remaining batter. Set aside.
Melt the blueberry jam on low heat in a saucepan, then spread evenly over the baked layer.
Gently spoon the remaining batter evenly over the blueberry jam. Evenly sprinkle the top with the macadamia nuts.
Bake uncovered for 30-35 minutes more, or until the nuts are beginning to brown and the top layer is golden brown and firm.
Like a cookie, it will continue to cook and harden after removing from the oven, so be sure not to overbake it.
Let cool and then cut into squares or bars. It will keep in an airtight container for 1 week. They can also be frozen.