Pre-heat oven to 170ºC. Lightly grease and line a 23cm spring-form cake tin.
Using an electric beater cream butter and sugar until light and fluffy then beat in eggs one at a time beating well between each.
Remove from the beater and fold in sour cream, sifted flour and baking powder and lemon zest. Spoon into prepared tin and bake for 40-50 minutes until risen, golden and a skewer can be removed cleanly from the centre.
Let cool for 10 minutes then spoon over lemon syrup.
For lemon syrup simply combine sugar and lemon juice and stir until sugar dissolves. Let cake cool completely then slice into three layers.
For filling combine crème fraiche, cream and vanilla paste and whisk until thick and silky. Sweeten with icing sugar if desired.
Divide cream between cake layers (keep any excess for serving) and spread evenly before sandwiching together. Chill until serving.
For honey syrup oranges combine orange slices, honey and water and simmer 5-8 minutes until syrupy and glossy.
Serve cake sliced and drizzle with orange honey syrup.