Add the passion fruit pulp, sugar and lime juice to a saucepan. Bring to a simmer, stirring until the sugar dissolves. Take off the heat and let it cool down completely.
Preheat the oven to 320°F/160°C. Mist an 8-inch deep cake pan with cake release and line with baking paper. Sift the self raising flour into a mixing bowl. Add the sugar and stir to combine.
Add the cubed butter and rub it in with your fingertips to create a fine breadcrumb consistency.
Add the milk, passion fruit pulp, eggs and vanilla. Stir to combine until the batter is smooth. Pour the batter into the prepared pan and level.
Bake for 40-45 minutes, or until the cake is golden and feels firm to the touch. A skewer inserted in the centre should come out clean.
Run a knife around the edge of the cake tin and gently turn the cake out onto a wire rack. Make sure the cake has cooled completely before slicing in half horizontally.
Place the mascarpone, heavy cream, powdered sugar and vanilla bean paste into a mixing bowl. Beat until the frosting holds peaks. Stir in passion fruit pulp and keep chilled.
Put the bottom cake layer on a plate and brush with syrup. Spread with frosting and sandwich with the top layer.
Spread remaining frosting on top and swirl it. Drizzle with passion fruit syrup. Decorate and serve!