Trim the fennel, reserving a handful of green fronds. Cut into slices about 1/2 cm thick. Heat a little olive oil in a sauté pan, and, working in batches and seasoning with salt and pepper as you go, fry the fennel on both sides until golden and tender. As the fennel is done, arrange it on a serving platter.
Zest the orange and set the zest aside. Remove the skin with a sharp knife, taking care to remove all the white pith from the fruit. Discard the peel. Cut out the orange sections, arranging over the fennel, and squeeze the orange juice over the whole salad.
Slice the onion into paperthin rings and arrange over the salad. Scatter over the olives and pine nuts. Squeeze over lemon juice to taste. Drizzle over a little more olive oil. Finally, scatter over the reserved fennel fronds. Serve.