I long for him most 
during these long moonless nights. 
I lie awake, hot, 
the growing fires of passion 
bursting in my heart.

Another translation by Kenneth Rexroth:

You do not come 
On this moonless night. 
I wake wanting you. 
My breasts heave and blaze. 
My heart burns up.

Another translation:

I would meet him
But there's no way, so on this moonless night
From my yearning the embers of my love
Send sparks leaping in my breast,
Setting my heart aflame. 


Source: http://www.poemhunter.com/poem/i-long-for-him-most/

Thinking about him

I slept, only to have him
Appear before me
Had I known it was a dream
I should never have wakened

Translation: Donald Keene
"But, while only 18 of Ono no Komachi's tanka survive, among these thousands of others, they are, for me, among the most memorable.  They use the form to generate both passion and philosophical insight. "


Further reading
http://www.washburn.edu/reference/bridge24/Komachi.html