Preheat the oven to 180?C. Line a cookie tray with baking paper.

Cream the butter and sugar with an electric mixer or food processor until fluffy and light. Add the egg, zest and vanilla, and mix for 1 minutes until creamy. Sift in the flour, baking powder and salt, then add the ground almonds and mix briefly to form a dough. Chill the dough for 20 minutes to firm up enough for rolling.

Roll the dough between 2 pieces of baking paper to a thickness of 4mm. Use a 5mm cookie cutter to cut rounds from the dough. In half of the biscuit rounds use a 2cm cookie cutter [or bottle top as I did] to make the holes in the center. Re-roll any offcuts. Use a metal spatula to carefully arrange the rounds on the lined tray with space between each to allow for spreading. Bake for 12-15 minutes until lightly golden. Use a metal spatula to carefully move the cooked biscuits to a cooling rack [if using GF flour they may be a little crumbly so be gentle, they will firm up as they cool]. Once completely cool spread the jam onto the bottom biscuits and top each with a 'holey' biscuit for the jam to peep through.

Store in an air-tight container and eat within 3 days.