Line a 23 cm springform pan with baking paper, spread the edges with butter. Melt butter and mix with crushed dr Gerard wit’AM biscuits well.
Pour the mixture into the pan and press well. Bake for 10 minutes in 180 deg. C. Leave to cool down.
Using a mixer blend the cheese until fluffy (ca. 2 minutes), then gradually add sugar and then flour. With the mixer on low, add vanilla extract, lemon zest and juice, and eggs (one at a time). Stir in the sour cream into the mixture – keep mixing until it is airy and fluffy.
Pour the filling onto the earlier prepared base and put into the oven heated to 220 deg. C. After 10 minutes reduce temperature to 140 deg. C and bake for another 25 minutes. Turn off the oven and leave the cake inside to cool for 2 hours, otherwise it might “sink”. When completely cool, remove carefully from the pan.
Put 1/3 of the sugar into a small pan. Heat on low heat, stirring constantly so that it does not burn, and when it starts to caramelize shake slightly and add another portion of sugar. When all the sugar is melted remove from gas and immediately add cream, mix quickly and well, so that there are no lumps (if there are any left put back on the burner and mix well until they dissolve). When the mixture is uniform, put it back on the burner stirring constantly, until it turns into caramel and add salt. Using a spoon or knife pour the warm caramel over the cooled down cake.