- Preheat oven to 180˚C (350˚F).
- In large bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
- In food processor or blender, process beets, buttermilk, cocoa powder, and vanilla into a puree. Set aside.
- Use a hand-mixer to beat butter in a bowl until soft and then beat in sugar until fluffy. Beat in eggs, one at a time, incorporating each one before adding next.
- With mixer on low, alternately beat in reserved dry mixture in 3 parts with wet mixture in 2 parts, starting and ending with dry. Scrape bowl as needed between additions.
- Scrape batter into greased and floured 23 cm x 13 cm / 9 x 5 in. (1.9 L) loaf pan, smoothing top.
- Bake 45 to 50 minutes or until a toothpick comes out clean when inserted into centre. Cool cake completely in pan on wire rack.
- Meanwhile, drain ricotta in cheesecloth-lined, fine-mesh sieve. Squeeze to remove excess moisture. Transfer ricotta to food processor and pulse until smooth.
- Add butter; pulse until light and fluffy.
- Add icing sugar and vanilla; pulse until smooth (if icing is too soft, refrigerate 10 to 15 minutes to firm it up). Spread icing over top of cooled cake.
- Refrigerate 2 hours or until icing is firm. Store in fridge in airtight container up to 2 days.
Garnish cake with raspberries if you like.