Preheat the oven to 220°C, fan 200°C, gas 7. Place the mackerel fillets skin-side down on a baking tray.
Tear the bread into chunks and whiz in a small food processor or a mini chopper until it forms coarse crumbs. Tip the breadcrumbs into a small bowl, add the parsley and the sunblush tomatoes and mix together well.
Pile the breadcrumb mixture on top of each of the mackerel fillets, patting it down well. Bake in the oven for about 12-15 mins, until the fish is cooked through and the topping is golden brown.
Meanwhile, lightly peel the cucumber then halve lengthways. Scoop out and discard the seeds, then thickly slice the cucumber into crescents. Toss together with the cherry tomatoes and salad cress.
For toddlers, serve a crispy-crumb mackerel fillet with the chunky salad on the side. Let them squeeze a lemon wedge over the top if they like.
Cook's tip: for baby, skin the cooked mackerel fillets and mash with a little of the breadcrumb topping. Serve the cucumber and tomato on the side, if your baby is old enough for finger food.