Cream butter and sugar until light in colour and fluffy. Add eggs one at a time, beating well after each addition. Beat in sour cream, vanilla and lemon zest. In a separate bowl, whisk or sift together flour, baking powder, baking soda, cardamom and salt. Add to liquid ingredients, stirring gently until completely incorporated and smooth, but don’t over mix. Spoon half the batter into a greased and floured 10-inch bundt pan. Combine brown sugar and cinnamon and sprinkle half this mixture over top of the batter. Cover evenly with blueberries, then spoon on remaining batter. Smooth the surface and sprinkle with remaining brown sugar-cinnamon mix. Bake at 350°F for 1 hour or until tester inserted in the middle comes out clean. Remove from oven and cool in pan for 10 minutes, then turn out onto wire rack to finish cooling.