Both HNO3 and Ca(OH)2 are strong acid/base so they completely dissociate in solution.
First you need to find the amount of OH- that needs to be neutralized:
2.0 M Ca(OH)2 * 500 mL Ca(OH)2 * [2 mol OH / 1 mol Ca(OH)2] = 2 mol OH-
Therefore, you need 2 mol H+ to neutralize the solution:
2 mol H+ * [1 mol HNO3 / 1 mol H+] * [1 L HNO3 / 1 mol HNO3] = 2.0 L of the 1 M HNO3
*** Note that in the third term in the step above is the inverse of the given HNO3 molarity. Sometimes inverting units in stoichiometry is useful and completely fine to do so.***