Preheat the oven to 350 degrees F and lightly grease an 8×8-inch baking pan with butter or margarine.
In a medium-sized bowl, sift together flour, sugar, salt, baking powder, and baking soda. Add in margarine and mix until crumbly.
In a separate bowl, whisk together eggs, evaporated milk, and vanilla extract until well combined.
Add wet ingredients to the dry ingredients and mix just until combined (don’t over-mix). Pour the batter into the prepared baking pan and bake for 25 minutes or until a toothpick inserted comes out clean.
Let cool completely before serving.