Preheat your oven to 200°C/Fan 180°C/Gas 6. Trim the roots and woody tops from the fennel and cut roughly into 1cm slices. Chop the tomatoes into small wedges. Scatter both onto a large roasting tin and toss with 1 tbsp oil and a generous pinch of salt and pepper. Slide into the oven for 20 mins, till golden and tender.
Meanwhile, pour 800ml boiling water into a pan. Crumble in the stock cube and stir well to combine. Set over a low heat.
Peel the onion and finely chop. Peel and finely chop the garlic cloves. Pick the rosemary leaves and finely chop. Roughly chop the black olives.
Pour 1 tbsp oil into a large pan and warm to a medium heat. Slide in the chopped onion, garlic and rosemary. Sprinkle in 1 tbsp fennel seeds and a pinch of salt and pepper. Fry for 3-4 mins, stirring occasionally, till slightly softened.
Stir in the risotto rice, and continue to cook for 1–2 mins, till the rice makes a slight popping sound. Pour in 1 ladleful of hot stock and use a wooden spoon to keep the rice moving till all of the water has been absorbed.
Repeat the stock ladling and stirring process till only 1 ladleful of liquid remains and the rice is swollen and nearly cooked – about 20 mins. By now the vegetables should have roasted. Stir the vegetables into the rice along with the baby leaf spinach and chopped olives, till the spinach leaves are slightly wilted. Add the final ladle of stock and stir in.
Squeeze half of the lemon juice into the risotto. Have a taste of the rice, and add more salt and pepper if needed. Spoon the risotto onto plates and serve with wedges of the remaining lemon half for squeezing.