• Heat the oven to 350°F (180 °C). Lightly grease an 8x8 inch (20 cm square) pan and line the base with baking paper. Leave an overhang of paper so you can lift out the baked cake.

Cake batter

• In a medium bowl whisk the flour, baking powder, baking soda, salt, and poppy seeds. Set aside.190 g all-purpose flour, 1 1/2 tsp baking powder, 1/2 tsp baking soda, 1/2 tsp salt, 1 1/2 tbsp poppy seeds
• In a large mixing bowl rub the lemon zest into the sugar with your fingertips until the sugar smells really citrusy. Add the softened butter and beat with a handheld mixer (or a whisk and elbow grease) for about 2 minutes until light and creamy. 150 g granulated sugar, 2 tablespoons lemon zest, 113 g unsalted butter
• Beat in the eggs one at a time, scraping down the bowl as needed. Mix in the vanilla, then the lemon juice and yogurt. The mixture may look a little curdled at this stage but it will smooth out once the dry ingredients go in. 2 large eggs, 2 tablespoons lemon juice, 1 tsp vanilla paste, 180 g Greek yogurt
• Tip the dry mix into the wet and fold gently with a spatula until just combined. Stop as soon as you no longer see streaks of flour. The batter will be thick.
• Spoon the batter into the prepared tin and smooth the top. Let the batter rest for 10 minutes on the counter while you make the streusel.

Streusel

• In a small bowl rub the lemon zest and sugar to release the lemon oils. Whisk in the flour, poppy seeds and salt. Pour in the melted butter and stir with a fork until clumps form. Pop the bowl in the fridge while you make the batter. 100 g granulated sugar, 1 tbsp lemon zest, 95 g all-purpose flour, 1/2 Tbsp poppy seeds, Pinch of salt, 75 g unsalted butter
• Scatter the chilled streusel evenly over the surface, pressing some of it together to make bigger clumps.
• Bake for about 40-45 minutes until the streusel is golden and a skewer inserted into the center of the cake (through the crumb, not just the topping) comes out clean.
• Leave the cake to cool for 15 minutes before removing from the pan onto a wire rack.
• While it cools, whisk the icing sugar with lemon juice until you have a thick, pourable glaze. Add the extra juice drop by drop if needed. Drizzle the glaze over the warm cake. Leave to cool before cutting. 60 g powdered sugar, 1/2-1 Tbsp fresh lemon juice