Preheat the oven to 350°F (180 °C). Line a 9 × 5-inch loaf pan with parchment paper, leaving some overhang on the long sides.
Cream the butter and sugar. Beat 1 cup + 2 tablespoons (9 oz / 255 g) unsalted butter and 1¼ cups (8.8 oz / 250 g) granulated sugar with an electric mixer for about 5 minutes, until pale and fluffy.
Add the eggs. Beat in 3 large eggs, one at a time, mixing well after each addition.
Add the ricotta and flavorings. Mix in ¾ cup (6 oz / 175 g) whole-milk ricotta, 1 tsp vanilla extract, and the finely grated zest of 1 lemon until combined.
Add the dry ingredients. Add 2¼ cups (9.7 oz / 275 g) self-rising flour and ¼ tsp salt. Mix briefly, just until no dry flour remains. Do not overmix.
Add the blackberries. Toss 5½ oz (150 g) fresh blackberries with about 1 tablespoon of the flour before folding them gently into the batter. Reserve a few berries for the top if desired.
Bake. Transfer the batter to the prepared loaf pan and smooth the top. Bake for 45–50 minutes, or until golden and a toothpick inserted into the cake (away from a blackberry) comes out with a few moist crumbs but no wet batter.
Cool. Let the cake cool completely in the pan before removing it. Transfer to a wire rack and cool completely before slicing.
Add the glaze, if using. Whisk ¾ cup (3 oz / 100 g) powdered sugar with 1–2 tsp fresh lemon juice until you have a thick but pourable glaze. Drizzle over the cooled cake and garnish with fresh blackberries.