Pre-heat oven to 350 Deg F. Grease a 10 cup bundt pan well. Use a spray with flour in it or brush well with DIY bundt pan release ( see blog post for details).
In a medium bowl sift together the flour, baking powder and baking soda 2 times. Whisk in the salt and hibiscus powder. Set aside
In a large mixing bowl cream the butter until light and fluffy 3-4 minutes. While this is mixing, measure the sugar into a bowl, then add the lemon zest, Rub between your fingers until the zest is well mixed with the sugar. Add this to the butter and mix again another 3-4 minutes. Add in the eggs one at a time, mixing well between each, scraping down the sides of the bowl when necessary.
Using the bowl the sugar was in, whisk together the lemon juice, vanilla extract and sour cream. Alternate adding this mixture with the flour mixture until just combined and no flour streaks remain. Stir a few times with a spatula to get everything from the bottom of the bowl mixed in.
Pour the batter into the prepared bundt cake pan and smooth the top. The bundt pan should be about a little over ¾ of the way full. You don’t want it all the way filled.
Bake for 60 minutes or until a toothpick or skewer inserted into the middle comes out clean. Let cool for 10 minutes then invert onto a wire cooling rack. Let cool completely before transferring to a plate or cake stand, before adding the icing.