To do this, clean the broccoli and cut into small florets.
Peel the green asparagus in the lower third and cut into pieces approx. 5 cm long.
Peel the onions and cut into fine rings.
Bring the vegetable stock to a boil in a saucepan and first add the asparagus pieces and cook covered for about 5 minutes over medium heat.
Then remove the asparagus pieces with a sieve spoon and let cool on a plate.
Now add the onion rings to the vegetable stock and cook for 2 minutes. Then add the broccoli florets and cook for 1 minute.
Drain the onion and broccoli over a sieve and collect the broth. Add both to the asparagus pieces and let cool down.
For the dough, mix the flour, rye meal, baking powder and salt in a mixing bowl, add about 5 tablespoons of cold water and add the chilled butter in pieces and knead everything with the dough hook to form a smooth shortcrust pastry.
Put the dough in a greased and floured tart pan, spread the baked peas on top and prebake in the oven at 180 ° C (or 200 ° C top / bottom heat) on the middle rack for about 10 minutes. Take out and let cool down a bit.
In the meantime, whisk the eggs, sour cream and 100 ml of the collected vegetable stock in a bowl. Season to taste with salt, pepper and the herb mix.
Now distribute the asparagus, broccoli and onions nicely on the pre-baked, slightly cooled tart base, pour the herb cream over it and bake for another 30 minutes at 180 ° C (fan oven) or 200 ° C (O / U) on the middle rack.