In a small heatproof bowl or jar combine 1/4 cup apple cider vinegar, 1/4 cup water, 1 tsp granulated sugar and 1/4 tsp salt. Stir until sugar and salt dissolve.

Add the thinly sliced red onion to the jar, press down so liquid covers the onion. Let sit at room temperature for at least 20 minutes. For best flavor, refrigerate 1 hour. These will keep up to 2 weeks refrigerated.

Salted cucumber (quick-salt)

Thinly slice the cucumber. Place in a bowl, sprinkle with 1/2 tsp coarse salt, toss and let sit for 10 minutes to draw out excess water.

After 10 minutes, gently squeeze cucumber slices or blot with paper towel to remove excess moisture. Reserve for sandwich assembly.

Sandwich assembly

Prepare the bialy: if desired, split the onion bialy horizontally and lightly toast cut sides under a broiler or in a skillet for 1–2 minutes until just golden and warmed.

Mash the avocado: scoop the flesh from half an avocado into a small bowl. Add 1/2 tablespoon lemon juice, 1/2 teaspoon olive oil, 1/4 tsp salt and 1/8 tsp black pepper. Mash with a fork to a spreadable consistency (some small chunks remain).

Spread the mashed avocado evenly on the bottom half of the toasted bialy.

Layer 1/2 cup mixed greens on top of the avocado, arranging so they cover the surface.

Top the greens with the salted cucumber (about 1/2 cup), then add 1/2 cup shredded or ribboned carrot evenly over the cucumber.

Drain the quick pickled red onions and scatter about 1/4 cup over the carrots. If using, sprinkle 1/2 tsp sesame seeds and 1/4 cup microgreens or cilantro.

Taste and adjust: if any component needs more brightness, drizzle up to 1/2 tsp lemon juice or a small pinch of salt. Close the sandwich with the top half of the bialy.

If packing as a boxed lunch: wrap tightly in parchment or foil to keep together. Pack any leftover pickles separately to keep the bialy from getting soggy.