In a large bowl, combine flour, salt, baking powder and baking soda. In a separate bowl using a mixer, beat butter until light and fluffy. Add sugar and vanilla to bowl and beat well to combine. Beat in eggs, one at a time. Add half the dry ingredients to the butter mixture and mix until combined, then add half the buttermilk, mixing well to combine. Add remaining dry ingredients, mixing well to combine, followed by remaining buttermilk, mixing well to combine. Mix in cream of coconut.