In wide saucepan, pour in enough salted water to come 2 inches (5 cm) up side. Add lemon slices, squeezing juice into water; cover and bring to simmer over medium heat. Slide salmon into pan; cover and return to simmer. Simmer until salmon flakes when tested but is still slightly translucent in centre, about 4 minutes. Transfer salmon to plate; let stand for 5 minutes. Refrigerate until cold, about 1 hour.

Meanwhile, cut green stalks from fennel, reserving fronds. Using knife or mandoline, slice fennel thinly. In bowl, toss fennel with 1/2 tsp (2 mL) of the salt. Let stand until fennel releases some of its moisture, about 30 minutes. Using hands, squeeze out excess moisture and transfer to large sieve or fine colander.

Meanwhile, in separate bowl, cover red onion with water and let stand for 30 minutes; add to fennel in sieve. Rinse fennel and onion; pat dry thoroughly. Transfer to clean bowl with radishes.

In small bowl, whisk together olive oil, vinegar, lemon juice, garlic, remaining salt and pepper. Drizzle 1/4 cup (60 mL) of the dressing over fennel mixture; toss and let stand for 15 minutes. Scrape onto serving platter. Top with salmon fillets; drizzle salmon with remaining dressing. Chop enough reserved fennel fronds to make 3 tbsp (45 mL); sprinkle over salmon.

Makes 4 servings.