Make the turmeric pickled onions: In a small bowl, combine the onion, vinegar, ½ teaspoon salt, turmeric, and ½ cup cold water. Cover and store in the refrigerator while you prepare the rest of the recipe. They can also be made and refrigerated up to one week in advance.
Make the tahini sauce: In a food processor or blender, purée the tahini paste with the lemon juice and zest until smooth. Gradually add in ½ cup cold water and continue to process until the mixture reaches a pourable consistency. Season with salt and pepper. Transfer sauce to a small bowl and set aside at room temperature, or cover with plastic wrap and store in the refrigerator for up to one week.
Make the vegetables: Generously salt a large pot of water and bring to a boil. Then, add the green beans, and cook until just tender, about 4 to 5 minutes. Drain and rinse with cold water to cool. Set aside, still in colander.
Heat the olive oil in a large skillet over medium-high. Add the mushrooms and cook, stirring occasionally, until golden, about 5 to 6 minutes. If the mushrooms release any liquid, drain and discard it, then return to the heat. Add the garlic and cook, stirring, 1 minute. Add the blanched green beans and toss with the mushrooms until just warmed through.
Transfer the green beans and mushrooms to a serving dish and drizzle with the tahini sauce. Drain pickled onions well, and sprinkle over the dressed vegetables. Garnish with almonds and serve.