Preheat oven to 350°F (180°C). Grease a 9-inch (2.5 L) round cake pan with cooking spray. Whisk flour with cocoa powder, baking soda and salt in a large bowl. Whisk eggs in a separate bowl, then whisk in sugar, oil and vanilla. Scrape egg mixture into flour mixture and stir gently until just combined. Add water and stir well. Scrape into prepared pan. Bake 30 to 35 minutes or until a cake tester inserted into centre comes out clean. Let cool in pan on rack for 10 minutes and turn out onto rack to cool completely.
Heat whipping cream to a simmer in a small pot. Add chocolate, remove from heat and stir until melted. Stir in olive oil and rosewater (if desired). Cool for about 10 minutes; pour evenly over cake.
Nutrients per serving: 414 calories, 4.8 g protein, 17.4 g fat (8.1 g saturated fat), 63.5 g carbs (4.3 g fibre), 127 mg sodium