Pulse ¾ cup herbs in a food processor until finely chopped. Add butter, lemon zest, 2 tsp. lemon juice, 1 tsp. salt, and ½ tsp. pepper. Pulse to bring together.
Place radishes in a medium bowl; drizzle with a little lemon juice and add a pinch of salt. Toss to combine.
To serve, spread toast with herb butter and top each with a fried egg. Scatter dressed radishes over top along with a few sprigs of herbs.
Herb butter can be made 1 week ahead. Cover and chill.
