Preheat the convection oven to 175 degrees Celsius and grease a 23cm circular cake pan with non-stick spray.
Sift the flour, 200g sugar, baking powder, and salt into a primary mixing bowl.
In a separate vessel, whisk the eggs, vegetable oil, milk, and vanilla extract until fully emulsified.
Gradually incorporate the liquid mixture into the dry ingredients, stirring until a homogenous batter is achieved.
Gently fold the 200g of diced strawberries into the batter using a silicone spatula to prevent maceration.
Transfer the batter to the prepared pan and bake for 30 to 35 minutes, or until a probe inserted into the center emerges clean.
While the cake is baking, combine the halved strawberries, 50g sugar, and lemon juice in a saucepan over medium heat.
Simmer the sauce for 10 minutes until the fruit softens, then whisk in the cornstarch slurry and cook for an additional 60 seconds to thicken.
Allow the cake to cool on a wire rack for 15 minutes before slicing and topping with the strawberry sauce.