Preheat oven to 180C and line a springform cake tin with baking paper.
Sprinkle sugar at the base and arrange mandarin segments in a spiral. Slice any large segments in half.
In a large bowl, combine flour, almond meal, sugar, baking powder and salt, then add mandarin juice, milk, oil, vanilla and vinegar. Mix until there are no lumps, then add poppyseeds and stir.
Pour batter into tin and bake for 50-60 minutes or until a skewer comes out clean.
Allow cake to cool in the tin, then remove, flip over cake so the mandarin spiral is on top and peel off baking paper.