This is no ordinary avocado toast. Add smoked salmon and serve the whole thing on a bagel for a substantial meal that you'll want to eat with a knife and fork. Smarts: We couldn't resist adding the option of sprinkling Everything Bagel Seasoning on top of this dish. This seasoning mix is becoming more widely available and there are plenty of recipes online, but feel free to skip it if you prefer.
Toss arugula with second portion of lemon juice, olive oil (portion for avocado toast), and Everything Bagel Seasoning. (If not using seasoning, season with some salt and pepper.)
Set bagel halves out on serving plates, cut-side up. Spread each half with mashed avocado. Top with salmon and arugula.