Begin by preheating the oven to 350 F. Grease a round 9 or 10 inch cake pan with non-stick spray, butter, or olive oil.
In a large mixing bowl, mix your olive oil, milk, lemon juice, egg, yogurt, lemon extract, baking powder, baking soda, and agave or sugar together. Once this mixture is creamy and smooth, add your flour and mix until a fluffy batter is formed.
Transfer the batter into your greased cake pan and use a silicone spatula to ensure it's even. Bake in the oven for 30 minutes.
While the olive oil cake bakes in the oven, prepare your powdered sugar for dusting on top and your blackberry syrup to drizzle. To make the blackberry syrup, bring a small saucepan to medium heat. Add the blackberries, water, and sugar, and cook, stirring, until the blackberries are bubbling. Remove the saucepan from the heat. Strain the pulp from the blackberry syrup and store the blackberry syrup in a jar until you're ready to serve.
Remove the cake from the oven and allow it to cool completely. Dust the top of your olive oil cake with powdered sugar. Serve each slice with whipped cream and blackberry syrup drizzled on top. Enjoy!