Divide bread among 4 large shallow serving bowls. 

 

Finely chop together fennel stems and fronds (save bulb for another use).

 

In a large Dutch oven or heavy pot with lid, heat 3 tablespoons oil over medium heat. Add chopped fennel and clams; increase heat to medium-high and cook, covered, just until clams open, 7 to 8 minutes. Using a slotted spoon, transfer clams to serving plates with bread, then, reserving pot, strain juices through a fine-mesh sieve into a bowl. Spoon juices over clams. 

 

To the pot, add remaining 2 tablespoons oil and garlic; heat over medium-low heat until oil is fragrant and warmed, about 4 minutes. Add tomatoes and pinch salt, increase heat to high and cook, shaking pan back and forth once or twice, until tomatoes are collapsed with some of their juices released, 1 to 2 minutes more.

 

Drizzle clams and toast with oil, then tomatoes and their juices on top. Sprinkle with salt and pepper.