Fennel, White Bean and Tuna Bruschetta

Fennel
3 tablespoons olive oil
1 large fennel bulb, thinly sliced
1 small red onion, thinly sliced
2 cloves garlic, crushed
2 teaspoons finely chopped rosemary
sea salt

White beans
2 tablespoons olive oil
1 x 400 gram tin cooked white beans, drained and rinsed
2 cloves garlic, crushed
1 teaspoon finely chopped rosemary
1 handful rocket, chopped
zest and juice 1 lemon
2 tablespoons sour cream
¼ cup freshly grated Parmesan

To assemble
1 piece preserved lemon
2 x 185 gram tins tuna, drained and flaked
4 halves sundried tomato, thinly sliced
½ cup pitted black olives
1 handful rocket
1/3 cup picked flat-leaf parsley
4 large slices sourdough bread, grilled or toasted