Preheat oven to 180 degrees C. Grease a 20x30cm baking pan.
In a medium bowl, stir together the flour, sugar, bicarb soda and salt. Add the eggs, oil, pineapple and vanilla, mix until well blended. Pour into the prepared pan.
Bake for 30 to 35 minutes in the preheated oven, until a toothpick inserted comes out clean.
To make the topping: In a small saucepan, combine 1/2 cup sugar, pecans, butter, evaporated milk, 1 teaspoon vanilla and 1 cup coconut. Cook over medium heat, stirring occasionally, until the mixture thickens. Poke holes in the cake with a fork then pour the warm mixture over the cake.