Make candied beetroot. Place sugar, glucose and 2 cups (500ml) water in a heavy-based saucepan; bring to the boil. Add sliced beetroot; cook over low heat for 40 minutes or until beetroot is translucent (lift a piece from thick syrup using tongs to check if it is translucent); keep checking the heat as you may need to increase it as syrup thickens. Using tongs, transfer beetroot to wire racks to cool. Simmer remaining liquid over low heat for 5 minutes or until reduced and syrupy. Cool.
Preheat oven to 180°C/350°F. Grease a 25cm x 37cm (10in x 14¾in) rectangular slice pan; line base and long sides with baking paper.
Grate beetroot coarsely; you will need 2½ cups. Place beetroot in a food processor with buttermilk, oil and vinegar; process until as smooth as possible.
Beat butter and sugar with an electric mixer until light and fluffy. With motor operating, add one egg at a time, beating well after each addition. Beat in vanilla.
Sift flour, cocoa powder, soda and salt into a medium bowl. Add dry ingredients to butter mixture, alternating with buttermilk mixture, beating on low speed until well combined; do not over-beat. Spread batter in pan.
Bake cake for 25 minutes or until a skewer inserted in the centre comes out clean. Leave cake in pan for 5 minutes; transfer to a wire rack to cool completely.
Meanwhile, make cream-cheese frosting. Beat butter and cream cheese with an electric mixer until light and fluffy. Beat in sugar and vanilla. Cover; refrigerate until required.
Spread frosting over top of cake, creating a swirled effect. Top with candied beetroot and drizzle with a little syrup.