Cook the asparagus and beans in a pan of boiling water for 3 minutes. Drain, then cut into 4cm lengths. Toss together in a bowl with the radishes, tomatoes, cucumber, watercress and mint.
Heat a griddle pan. Brush the halloumi slices with ½ tbsp olive oil and grill for 2 minutes on each side.
Whisk the remaining olive oil together with the lemon zest and juice and the sumac. Toss the warm halloumi through the salad, drizzle over the dressing and serve with the pitta fingers.