Preheat oven to 350ºF. Grease holds and set on a baking sheet.
In a small bowl, whisk together the almond, pistachio, buckwheat flour and baking powder and set aside.
In a stand mixer fitted with the paddle attachment, beat the butter and sugar on medium until well combined.
While the mixer is running on low, add the eggs slowly and mix until fully incorporated.
Change the mixer setting to stir and add the nuts and flour mixture.
Remove bowl from the stand and use a spatula to fold in the zest.
Pipe or scoop the batter into the molds, filling each close to the top edge.
Bake for 30—35 minutes. Remove from the oven and place on a wire rack to cool.
Make the syrup:
Add the sugar and orange juice to a small saucepan and heat to melt the sugar. Pour over the cakes, while still warm.
To make caramel:
Heat the cream and set aside.
To a deep pot, add the juice, glucose and the sugar and cook over medium-high heat until the sugar has melted. Continue to cook to a medium golden colour.
Add the warmed cream slowly to deglaze. It will bubble up, so a deep pot comes in handy. Remove from heat and stir in the butter immediately. Allow to cool a little before the orange extract.
When cooled, drizzle onto cakes and top with a mix of caramelized and roasted pistachios.