Preheat oven to 350 degrees.
Combine the almond flour, salt, baking powder, cardamom and ginger in a medium bowl, breaking up any clumps in the almond flour.
Peel the pears and slice lengthwise into eighths, removing the core and stem.
Stir together 2 tablespoons coconut oil and the maple syrup in a 9" cast iron skillet. Arrange the pear slices in a slightly overlapping circle around the pan, and finish with a few slices in the center. Sprinkle the pears with lemon juice and set aside.
In a large bowl, whisk together the coconut oil and eggs, then add the sugar and vanilla and mix well. Add half the flour mixture and stir gently to combine, then add the milk and the remaining flour mixture, stirring gently after each addition. Do mot over-mix.
Gently spoon the cake batter on top of the pears, smoothing out to the edge of the pan and making sure the cake batter fills in around the pears.
Bake until the top is a deep golden brown and a skewer inserted in the center comes out clean, about 40 minutes. Place the cake on a rack to cool for five minutes in the pan.
Run a spatula or knife around the edge of the pan and invert onto a cake plate, leaving the pan on the cake for 10 minutes. Carefully remove the pan. Serve warm or at room temperature.