Pre-heat oven to 175°C/350°F. Rinse the blood oranges thoroughly with hot water and, using a fine grater, grate the zest of 1/5 of the oranges. Reserve zest. Cut off the top and bottom of the blood oranges and carefully removing the peel if you’d like. Slice the oranges thinly, removing any of the pithy core.
In a small pot, add one third of the softened butter and melt, adding the brown sugar and stirring over medium heat with a whisk until sugar is fully dissolved. Add the thyme leaves and simmer for approx. 3 min. Spread the butter-sugar-thyme mixture evenly over the bottom of a springform pan and lay the blood orange slices over in a single layer.
In a medium bowl, combing flour, baking soda, and salt. In a large bowl, mix the remaining butter with granulated sugar, milk, ground ginger, and reserved blood orange zest for approx. 2 min using a hand mixer with beaters. Add the eggs in one at a time, and mix until smooth and silky, approx. 3 min. Carefully add in the flour mixture and beat until no more lumps are visible.
Pour batter over the blood orange slices and bake in a preheated oven for approx. 45 - 50 min. Remove the cake from the oven once done, and let it cool in the pan for approx. 10 min. Carefully invert it onto a serving plate, scraping any syrup residue from the pan and drizzling it over the cake. Served with freshly whipped cream and enjoy!