Preheat the oven to 200C/180C Fan/Gas 6. Line/grease an 8 or 9″ cake tin.
Make the crumble topping by combining all ingredients in a bowl, mash with a fork until mixture looks a bit like sand. Set aside.
Combine the olive oil, eggs and sugar in a large bowl or the bowl of a stand mixer. Mix on high for about 3 minutes, until everything has come together.
Add the lemon juice and zest and mix again.
Gently fold in the flour, ground almonds and baking powder until just combined. Pour batter into the cake tin.
Sprinkle over the crumble mix and bake on the middle shelf of the oven for 45-50 minutes, until golden on top and a skewer inserted comes out clean. (If you find the top is browning too fast, cover it with tin foil).
Let cool on a wire rack before dusting with icing sugar, slicing and serving with some cream or yoghurt (dairy free if preferred).