Step 1

To prepare salad: Whisk lemon juice, oil, garlic, cumin, chili powder, salt, and pepper in a medium bowl. Add cucumber, tomatoes, and avocado. Toss gently to combine and set aside to let the flavors blend.

Step 2

To prepare frittata: Place potatoes in a microwave-safe dish and cover with vented plastic wrap or lid. Microwave on High for 2 minutes. Stir and microwave, covered, until just tender when pierced with a fork, 1 to 3 minutes more.

Step 3

Meanwhile, heat 2 tsp. oil in a medium nonstick or cast-iron skillet over medium-high heat. Add mushrooms, sprinkle with salt and cook, stirring, until they release their liquid, about 3 minutes. Stir in spinach, scallions, thyme, and pepper; continue cooking until the spinach has wilted, 2 to 3 minutes more. Transfer to a plate to cool. Wipe out the pan.

Step 4

Once the mushroom mixture has cooled, whisk eggs and cottage cheese in a large bowl. Add the cooled mushroom mixture and the potatoes; stir until well blended.

Step 5

Add the remaining 2 tsp. oil to the pan and place over medium-high heat until it begins to shimmer. Quickly pour in the egg mixture. Cook, lifting the edges with a flexible heatproof spatula to allow uncooked egg from the middle to flow underneath, until nearly set, about 3 minutes.

Step 6

Cover the pan, reduce heat to low, and cook until the top is set and no liquid egg remains, 6 to 8 minutes.

Step 7

To release the frittata from the pan, run the spatula around the edge, then underneath, until you can slide or lift it out onto a cutting board or serving plate. Cut into wedges. Sprinkle the avocado salad with feta and serve with the frittata.