Thinly slice the red onion into very fine half-moons. Slice the lemon in half; reserve one half for juicing and the other half for garnish. Rinse and pat dry the capers. Coarsely chop the dill and set aside.

Prepare avocado

Halve the avocados, remove the pits, and scoop the flesh into a bowl. Immediately toss the avocado with 1 tablespoon lemon juice and a pinch (about 1/8 tsp) of sea salt to slow browning. Using a fork, mash the avocado to a slightly chunky but spreadable consistency.

Make dressing

In a small bowl whisk together the extra-virgin olive oil, remaining 1/2 tablespoon lemon juice, Dijon mustard, honey, the remaining sea salt (about 1/3 tsp), and freshly ground black pepper until emulsified. Taste and adjust seasoning—add more lemon or salt if needed.

Assemble stacks

On a serving platter, place a ring mold (3-inch round) or simply mound by hand. Spoon 2 to 3 tablespoons of the mashed avocado into each mold to form the base. Layer 2 to 3 thin slices of smoked salmon folded gently over the avocado. Sprinkle a small pinch (about 1/2 tsp) of chopped red onion and about 1/2 teaspoon capers over the salmon. Repeat for remaining portions. If using ring molds, gently lift mold straight up to reveal the stack.

Finish & garnish

Drizzle about 1/2 teaspoon of the dressing over each stack (reserve remainder for the greens). Scatter chopped dill and a few additional capers on top. Add a small handful (about 1/4 cup) of microgreens or baby greens alongside each stack and toss the greens lightly with the remaining dressing in a bowl before plating if you prefer them dressed.

Serve

Place baguette slices or crackers on the side. Garnish each stack with a small lemon wedge. Serve immediately so the avocado remains fresh.