Preheat oven to 350 °F (175 °C). Grease and line an 8×4″ loaf pan with parchment.

In a medium bowl, whisk flour, baking powder, baking soda, and salt.

In a mixer, beat sugar and eggs on medium for 2 minutes until fluffy.

Add melted butter, vegetable and lemon oils; mix until combined.

Stir in vanilla extract, lemon extract, lemon juice, and zest.

Mix in sour cream until just combined.

Gradually fold dry ingredients into wet mixture, mixing until just incorporated.

In a small bowl, toss blackberries with 1 tbsp flour, then gently fold into batter.

Pour batter into prepared pan and bake 45–50 minutes, or until a toothpick comes out clean.

Cool loaf in pan 10 minutes, then transfer to a wire rack to cool completely.

While cooling, whisk together powdered sugar, heavy cream, lemon juice, and vanilla to make glaze.

Drizzle glaze over cooled loaf and let it set before slicing.