In food processor, pulse flour and salt to combine. With motor running, gradually drizzle in hot water until mixture clumps together. (See Tip)
Remove dough to work surface and knead, folding it toward you and then pressing it with the heel of your hand; rotate. Repeat until smooth without adding any flour, 2 to 3 minutes (adding flour 1 tsp at a time if sticky).
Wrap in plastic wrap and let stand at room temperature for 30 minutes.
Divide dough into 6 even portions. Working with one piece of dough while keeping the rest covered, use the palms of your hands to roll it into a rope that's 1-cm (scant ½-in) thick. Cut rope into 1-cm (scant ½-in) pieces.
Using the tines of a fork (turned upside down), a sushi-rolling mat or a wooden cavatelli board, press each piece of dough toward you against the tines or grooves until it curls over itself to form a hollow shell.
In large pot of lightly salted boiling water, cook pasta until al dente, 2 to 4 minutes. Using a slotted spoon or spider, remove pasta to serving bowls. (This will ensure any excess semolina is left at bottom of pot.) Serve with a pasta sauce, like the 10-Minute Sugo or Thick & Glossy Pomodoro.