Zest and juice the lemon into a large bowl. Swirl in 1 tbsp olive oil.
Tip 1 tsp sumach into the bowl with the lemon and oil. Add a pinch of salt and a good crack of pepper. Whisk together to make a dressing. Set aside.
Using a vegetable peeler, shave thin whisps off the fennel. Trim and peel the carrots. Trim the courgettes. Peel them into ribbons, turning the veg as you go and stopping when you get to the core. Finely chop the cores. Peel ribbons off the asparagus too. Trim the radishes and finally slice them. Reserve the radish leaves.
Add all the ribboned veg to the bowl and toss together using your hands. Set aside to soak up the lemony marinade for a few mins.
Finely chop the dill, stalks and fronds. Roughly chop a handful of the radish leaves. Add the dill and the radish leaves to the ribboned veg. Toss together and serve straight away.