1 cup butter, at room temperature
In the bowl of an electric mixer or with a handheld mixer, cream the butter and granulated sugar together until light and fluffy.
Add the vanilla and egg yolks and beat for one minute.
In a separate bowl, whisk together the almond flour, plain flour, salt, cinnamon, and lemon zest.
Add the flour mixture to the wet ingredients and mix until just combined, stopping to scrape down the bowl as you go.
Divide the dough in half and press each half into a disc. Wrap the discs in plastic wrap and refrigerate for at least 30 minutes (you can do this a day or two in advance if you like).
When you're ready to bake, preheat the oven to 175 C.
Remove one disc of dough from the refrigerator. On a lightly floured surface, roll the dough out to 6 cm thickness. If your dough is sticking, keep dusting it with more flour and rolling until it feels right. If it softens too much, stick it back in the refrigerator for a bit. Using a 7.5 cm heart cookie cutter (or circular cutter), cut out as many cookies as you can manage. Keep re-rolling the dough until you run out.
Place the cookies on a parchment-lined baking sheet and put the sheet in the refrigerator to chill for 10 minutes. Chilling helps the cookies keep their shape when baking.
Repeat with the second disc of dough, but this time cut out your 7.5cm shapes, and then use a 5cm cookie cutter of the same shape to cut out the insides of the second set of cookies. Place on a parchment-lined baking sheet and chill for 10 minutes.
Bake the cookies for 12 to 15 minutes, or until lightly golden brown on the edges.
Remove the cookies from the oven and let cool. When ready to assemble, dust confectioners' sugar over the tops of the hollow shapes, leaving the solid shapes plain.
Using a small knife or spoon, spread jam over each of the solid shapes. Top each one with a dusted sugar cookie.