Trim the tops and bottoms off the beets. Rinse and scrub the beets to remove any mud or grit. Cut up any larger beets so that they are all about the same size.
Put the beets in a baking dish that's large enough to accommodate all of them in a single layer. Season with salt, then pour ¼ cup water into the dish. Cover tightly with foil and steam-roast until the beets are tender when pierced with a knife. Depending on the size, density, and age of the beets, this could take between 30 minutes and 1 hour.
Meanwhile, if you have greens to cook, heat a medium skillet over medium heat. Add a glug of olive oil, add the greens, and toss them until they are wilted, about 5 minutes., or less. Set aside until cool, then chop through them a few times if large.
When the beets are tender, let them cool until you can handle them, then rub or pare away the skins. Cut into ½-inch wedges or chunks and pile into a bowl. Add the greens.
While the beets are still warm, sprinkle with the vinegar, ½ teaspoon salt, and many twists of black pepper. Toss to distribute the seasonings and let the beets absorb the vinegar for a few minutes. Add a healthy glug of olive oil and toss again. Let the beets sit at room temperature until you’re ready to serve.
To assemble for serving, add the sunflower seeds, parsley, scallions, and pickled peppers and toss gently. Peel the avocados and cut them into neat chunks that are about the same size as the beet wedges, and add them to the beets, too. Toss thoroughly but very gently, so you don’t mash the avocado too much. Taste and adjust with more salt, black pepper, vinegar, or oil. Serve right away.