Heat the oven to 220°/ fan 200°C/ gas mark 7. Lay the bacon rashers on a foil-lined baking tray and cook in the oven for 15-20 minutes. After 5 minutes, add the tomatoes, brush the marmalade, sprinkle with the salad onions and season. Return to the oven for the remaining cooking time.
While the bacon and tomatoes are in the oven halve, stone and thickly slice the avocado. Finally, toast the bread and spread with butter.
Divide the bacon between the toast, and top with the avocado and roasted tomatoes. Serve immediately with some fresh spinach, if using.
Roasting the tomatoes with a touch of marmalade gives them a rich orangey sweetness. Tomatoes cooked in this way are perfect served on toast for a simple breakfast. try accompanying them with a soft scrambled or fried eggs, and serve with wafer-thin smoked ham rather than bacon, just for a change.