1. Place the avocado flesh, cream, and lemon juice in a bowl and use a hand mixer to purée until smooth. Season with salt and pepper to taste. Set aside.
2. Use a knife to remove any brownish bits from the salmon fillet, and then cut fillet into small cubes. Gently mix the salmon with all other tartare ingredients in a bowl. Season with salt and pepper to taste.
3. For a nice presentation, serve the tartare and avocado in layers using a cookie cutter. For each serving, start with the avocado purée on the bottom and top it with tartare. Press down gently before removing the cookie cutter.
4. Accompany with oven-toasted slices of baguette, lemon wedges, and microgreens of your choice.