So far as I know, he wasn't, just placed under house arrest.

According to Owen Gingerich's The Great Copernicus Chase, the 1633 decree calling Galileo to be interrogated* read, in part, as follows:

Galileo Galilei ... is to be interrogated concerning the accusation, even threatened with torture, and if he sustains it, proceeding to an abjuration of the vehement [suspicion of heresy] before the full Congregation of the Holy Office, sentenced to imprisonment....

(Emphasis added.) Gingerich goes on to say:

On the next page the results of the interrogation are recorded. In Italian are Galileo's words: 'I do not hold and have not held this opinion of Copernicus since the command was intimated to me that I must abandon it.' Then he was again told to speak the truth under the threat of torture. He responded: 'I am here to submit, and I have not held this opinion since the decision was pronounced, as I have stated.' Finally, there is a notation that nothing further could be done, and this time the document is properly signed in Galileo's hand. Galileo was sent back to his house at Arcetri, outside Florence, where he remained under house arrest until his death in 1642.

(Emphasis added.) These quotes can be seen using Amazon's "Look Inside" feature. This link worked for me. These passages are also excerpted in this pdf.

So, Galileo was explicitly threatened with torture, though he was not actually tortured and may not even have been "shown the instruments of torture" (which is the strongest claim made in reputable sources). As I argue in this thread, I believe that this justifies saying that the Church used torture (as an institutionalized practice) to force Galileo to recant.

* An earlier version of this comment referred here to "the 1633 sentence entered against Galileo" because I misread Gingerich's use of the word "sentence" to refer to a sentence of punishment, but he just meant a grammatical sentence ><.