This is a delicious Meyer lemon-almond cake which, like most upside-down cakes, is impressive to behold.
Preheat oven to 350 degrees. Rub bottom and sides of an 8-inch cake pan with 2 tablespoons butter and sprinkle bottom with sugar. Thinly slice lemons and remove seeds. Arrange lemon slices in concentric circles over brown sugar. Set aside.
In a food processor, pulse almonds until finely ground. Add baking soda and salt, and pulse to combine. In a medium bowl, whisk together egg yolks and honey. Stir in almond mixture.
Beat egg whites until doubled in volume (but do not form soft peaks). Gently fold whites into almond mixture until just combined. Transfer batter to prepared cake pan.
Bake until top is deep golden brown and a skewer inserted into middle comes out clean, 30 to 35 minutes. Let cool in pan for 5 minutes. Carefully turn out onto a serving plate. Serve warm or at room temperature. Slice with a serrated knife.