When you said, " she bakes", I think you're referring to your mother, purely by the context that this is about your childhood. When you look back on childhood, I think that parents are usually what we remember first.
It seems very early for me to say, lol, but I always look back on when I was (even) younger and think about how the trees were bigger, the night was darker, the days were brighter and full of fresh hope and games to be played. It's funny how easy it was to turn the shadows into ghosts and your own breathing into monsters. Even now I laugh at myself, so god knows how I'll be when I'm middle aged!
The last five lines were less upbeat and reminiscent. They were more about the now, though they refer to the past. They're more about the state of mind you grow into, whether it's real, or, as you said, in your mind. It's odd how we laugh at how, when we were little, we'd play pretend games, but, when we mature, so many problems come from what we invent in our heads.
A very clever, reflective piece, with lots of good talking points. Take care :)

Hello MA, the title 'Buttercream.' reminds me of my sister as she's started a little gluten free/dietary cake making business last year and it's really had lift off..

Whenever she bakes, I'm reminded of
home.
^
The 'she' in this line could literally mean anyone as many women bake, I would go for your mother purely because it reminds you of home but I guess it could be a friend or girlfriend or someone too... Being reminded of home is bittersweet for many of us and we always think of the good and bad memories as they all come through especially the good memories.

And not this house where I currently
reside, but the home of my childhood,
before I knew of palpable fears.
Back then, the only pain I felt was in
scraping my knee on the sidewalk and
spending too much time in the sun
and wanting to climb the massive rocks
lining the forest.
^
I like this stanza as many of us think we have it tough as a child yet skinned knees and broken bones (in some cases) are probably the worse things we suffer, then we become adults and it's heartache amongst everything else including paying bills; being adult is rubbish and I want to give up my membership haha.

The last time I traveled there, I noticed
that the rocks looked like pebbles,
only a few inches high, though I used
to imagine them as fortresses.
^
I like the differentiation from rocks turning to pebbles as you grew up for some reason it made me think of the vulnerability of children and how we as adults need to protect them the best we can although many children could teach us a thing or two.

My fears were laughable.
They were easily managed, a simple
"don't let the bed bugs bite" muttered
by my grandma every night like a prayer,
Cinderella wallpaper dancing around me.
^
Hindsight is a wonderful thing isn't it and our fears, as we grow older and wiser, are generally laughable but as a child they're huge aren't they? Although my fear of the dark heightened throughout adulthood for other reasons.. Now, with you mentioning your grandma here I'm wondering if she is the she in the first line, maybe? Love the image of cinderella wallpaper dancing around you.

I didn't know trouble then.
I was a good kid.
And now, the trouble's all in my mind.
And though I've committed no crime,
I don't feel good.
^
I put these lines together as they all interlink to make a big however, I feel this is saying we're all our own worse judge.

Lovely, sombre but a trip down memory lane.

Em x