Preheat oven to 375F degrees (185 celsius). Line standard 12-cup muffin tins with paper liners.
In a large mixing bowl beat together the sugar, olive oil and lemon juice until fluffy. Add the eggs and mix until well combined. Add the dry ingredients and stir until you get a smooth batter.
Add the chia seeds and blackberries and stir gently. With the ½-cup (you used to measure the oil), ladle the batter into the muffin liners.
Top each muffin with a blackberry and sprinkle with sugar.
Insert the tin into the oven and bake for 20 minutes, or until a toothpick inserted in the center comes out clean and dry. Let the muffins cool for 10 minutes on a cooling rack (Watch out! the blackberries are boiling hot!